25 March 2016

Self, Continuity, and Morality

Buddhists make a big deal about how disadvantaged people are by having the illusion of self. The rhetoric implies that having a sense of self is a severe disability. Since it is axiomatic that it is up to each of us to make progress on the path, it's further hinted that those who still have a sense of self are culpable for their own disability, as though we are simply not making enough effort. I find this a rather unattractive version of Buddhism. To my knowledge, the breakthrough to non-self has always been the preserve of a few who have the temperament for intensive practice and the opportunity to pursue it. No doubt some genetic and environmental factors are also involved, but this only reinforces that it always was and always will be a minority who make that kind of breakthrough. The idea that we all might make this breakthrough is a quaint dream.

On the other hand, this view overlooks the good that people with selves do, the great art that they have created, and the general advancement of humankind from science and technology (better health, longer life, lower infant mortality, less violence, etc). Buddhism implemented on a national scale, on the other hand, has almost always led to repressive, authoritarian politics, rigidly stratified societies, and entrenched privilege, along with poor standards of living, especially for the poor. So if we were looking for ways to save all beings from suffering, or at least reduce suffering for all beings, then the evidence suggests that Buddhist rhetoric is vastly overblown: basic education and healthcare is probably more effective. The eradication of polio has done more for the reduction of suffering in the world than Buddhism ever did.

This kind of discourse which sees self as a a disability is more prevalent now that it was when I became a Buddhist twenty years ago, partly because of the rise in prominence of Advaita Vedanta in Western countries or at least people who employ Vedantin methods of undermining the sense of self. Those who do this, like to refer to it as "Advaita" (non-dual), but I prefer to use Vedanta to keep it clear what kind of religious ideology underpins the methods and worldview associated with the approach. A Vedantin is typically seeking the non-duality between soul and God, two concepts foreign to Buddhism. While self-enquiry seems like a good idea, we also ought to be enquiring into the worldview espoused by Vedantins and asking why the Vedantin who claims to have no self talks about it in such different terms to the Buddhist.

Despite the popularity religious rhetoric around the evils of selfhood I remain deeply suspicious of it. I wrote a few essays on this theme in late 2009, including:
In these essays I expressed some of my doubts about the negative rhetoric around self. I tried to show how vital the development of a healthy ego is. One might, perhaps, transcend one's ego, but the idea that we could develop from scratch as human beings without an ego seems fanciful. A whole raft of behavioural and cognitive problems emerge from the lack of a well-defined sense of self. If the sense of self fails to develop in a person, or is compromised by disease or accident, then (contra the religious narratives) that person really is disabled. However good it might seem to lose your ego as an adult, having no ego to start with is uniformly disastrous. This seems never to be acknowledged or discussed by advocates of non-self.  I've argued that the problems ascribed to "egotism" seem more often to be the result of an under-developed ego rather than too much ego. I've also expressed doubts about the possibility of a functioning morality in the absence of a self (Ethics and Nonself in Relation to the Khandhas, 21 Mar 2014). I want to return to this last theme in this essay.

The different attitudes of Buddhist and psychological models partly relate to different definitions of what is meant by ego or self. Which definition we use is notoriously dependent on context and each context requires us to redefine the word. From the psychological side we may say that without what psychologists call an ego, no social interaction or learning is possible. Without a clear sense of self and other we do not develop empathy, for example. Without empathy we could not be moral because morality requires us to see our actions from another person's point of view and feel what they feel (or at least to imagine how they might feel). We also know that people who have personality disorders or other psychiatric problems can get into real difficulty if they take up meditation, particularly the kinds of meditation that undermine the sense of self. Generally speaking Buddhists have been quite reckless in seeing meditation as a panacea and not cognizant of how mental health problems manifest and how they affect a person's experience of meditation (I addressed this to some extent in my essay  Rumination, the Stress Response, and Meditation, 22 Jan 2016).

So what can Buddhists and Vedantins mean? How can we understand the no-self discourse in the context of contemporary knowledge about the brain and its role in what Westerners call "consciousness". The scare quotes are employed because I'm not sure that there is a cross-over between ancient Indian theories of cognition and modern theories which treat consciousness as an entity rather than a function or process. In other words I am inclined by my Buddhist studies to see consciousness as something we do, rather than something we possess.

Traditionally Buddhists use concrete nouns like "mind" (manas) or "thought" (citta), and action nouns like cognizing (vijñāna) "thinking" and "remembering" (smṛti) but they don't seem to use abstract nouns with respect to the mind. So even if a word like vijñāna can be made to mean "conscious", there is no equivalent abstract noun vijñānatva, no conscious-ness. So there is no abstracted faculty of mind under which concrete functions can be groups. In Buddhists texts the functions of the mind are most often grouped under a concrete noun "citta" rather than an abstract noun. These observations often seem trivial, but they point to a radically different worldview that separates us from the authors of the earliest Buddhist texts. They did not think like us at all.

Another big difference in how early Buddhists and Westerners understand the mind is metaphorical. In an earlier essay I tried to show that the MIND IS A CONTAINER metaphor, which is almost inextricable from the Western understanding of mental phenomena, is absent from Buddhist texts. Pre-modern Buddhist authors did not conceive of cognition as happening in the mind; nor thoughts, memories etc in the mind. Again, rather than being something we have, consciousness seems to be something that we do. For example it's might be phrased that the Buddha dwelled with a particular state of mind (iminā vihārena viharato) not in it.  Hence, I've also argued that where we might be tempted to translate "consciousness" in a Buddhist text, the phrase "mental activity" is almost certainly better (Manomaya: Background to Mind-Made Bodies. 28 Nov 2014).

Since my first forays into this field I have discovered the work of Thomas Metzinger, in which I find a very useful paradigm for thinking about selfhood. For example I wrote Origin of the Idea of the Soul (11 Nov 2011) and First Person Perspective (29 Apr 2011) exploring Metzinger's work and how I think it applies to contemporary Buddhism.

Metzinger draws on work by Antonio Damasio, amongst others, who I also refer to directly. Damasio has put forward the idea that what the brain does, in the first place, is model the internal milieu of the body for the purpose of maintaining optimal conditions for life. The inputs include information about blood pressure, blood sugar levels, hydration, hormone levels, balance and other forms of internal physical senses, and the state of the gut. The brain integrates these internal inputs with information from the senses about the environment and produces behaviour as a result. The view that this is all that the brain does is called Behaviourism. Behaviourism was a briefly popular theory of consciousness in the mid 20th Century. 

In a simple animal like the round-worm C. elegans (see Reflections on Living Things. 13 Nov 2013), Behaviourism may well be a sufficient account of the animal's behaviour. Though in a brain with only 302 neurons, it is still not entirely clear yet how it produces behaviour, and attempts to model the brain in a way that does produce behaviour are in their early stages. In more complex animals with millions or billions of neurons something more sophisticated is going on. As brains become more complex, with layers of organisational sub-units, emergent properties become apparent that cannot be predicted from the physiology of neurons. Sophistication of behaviour is correlated to some extent with brain complexity. Generally speaking more neurons with more connections, correlates to more complex behaviours. Though the relationship also has to take into account what subsystem the neurons are in. Neanderthals for example had significantly bigger and more complex brains than their ancestors, but most of the gain was in the visual cortex not in the neocortex. The increase went to improved eyesight, especially night vision, not to improved cognitive abilities generally. In anatomically modern humans, the gain in complexity was in the neocortex which does correlate with improved cognitive abilities. In particular Robin Dunbar has famously showed that there is a correlation between the ratio of neocortex to the rest of the brain and the size of social group an animal lives in. Out of this research came the famous Dunbar Numbers.

From the mapping of our internal milieu and via emergent properties we get the most basic sense of consciousness that all reptiles, mammals and birds seem to have. At least this seems to be the most plausible explanation. In fact we still do not know much about what consciousness is or how it is created by the brain. But neuroscience is a relatively young science (a few decades) and consciousness is a big problem. Consciousness, as neuroscientists generally conceive of it, is mainly concerned with moving around and seeking food and mates, but also forward thinking, learning from past experience, and social interactions. In some animals and birds the basic level of consciousness is the basis for an even more sophisticated simulation—a sense of being aware of what is happening, of ownership over the actions that result, of having a point of view—in other words a sense of self. Many animals, for example, recognise themselves in a mirror. One of the tests is to surreptitiously paint a dot on the forehead of the animal and see how they respond. The self-aware animal will look in a mirror, see the dot on their forehead, and try to touch their own forehead to feel what is there. 

One of the important findings from recent neuroscience is that when we study the many ways in which our sense of self can be compromised by disease, accident, surgery or even perceptual tricks (such as the rubber hand illusion or the virtual reality) we are led to the conclusion that our sense of self can only be a simulation or what Metzinger calls a virtual self model. If the self were "hardwired", i.e. if there were a definite structure or architecture associated with selfhood, such as there are for say visual processing or memories, this would be inconsistent with what we see in neurology cases.

The evidence also tells us that the sense of self cannot be divorced from the brain. For brain damage to affect the self the way it does, the self and the brain must be intimately associated. Because of this intimate association of the brain and the mind, physics at the mass, energy and length scales relevant to the functioning of the brain can now rule out other forces or types of matter than those already described. Of course other forces and types of matter may and do exist at other scales, but not on this scale. If there were such forces and they could interact with matter at this scale we'd be able to "see" that interaction and describe it. The fact is that we do not see it. And if we do not see it, then it cannot interact with the matter of the brain to play any role in the mind (see There is No Life After Death, Sorry, 23 Jan 2015). So the self and the mind cannot be wholly immaterial either.

We do not need to have all the specifics to draw broad conclusions about the mind and especially that part of the mind which is our sense of being someone, our first-person perspective. Despite the fact that many philosophers wish to hedge their bets, arguing that science is a social construct (or whatever), what we can do with evidence is eliminate certain types of explanations. As intuitive and attractive as other kinds of explanations for mind are, they simply do not explain what has been observed. The two extremes of physical-monism and dualism can be excluded from consideration because they do not generate the right kinds of answers. And this enables us to focus on the type of answers that are at least possible. There are still a range of these, but we do know that only a virtual self of some kind, generated by the brain in some way, fits the facts.

The current best explanation of the known facts is that the brain is creating a simulation of a self, integrating many streams of information into a first-person perspective. No one suggests that we fully understand the workings of the brain or how it generates a sense of self. Indeed some argue that theories of the mind have yet to explain anything. But any theory that eventually does explain the functioning of the mind will certainly not be a kind of physical-monism or involve substance dualism. And thus, for example, studying how neurons and brains work in a physical sense will not only be relevant to the study of the mind, it will be essential.

This is good news for Buddhists. As regular readers will be aware I am rather antipathetic to the idea that modern science confirms ancient wisdom. For example, I think there is no genuine connection between Buddhism and quantum mechanics. As far as I can see, claims to the contrary are bunk based on a superficial understanding of both Buddhism and quantum mechanics. Just because two bodies of knowledge can be counter-intuitive does not mean that they are in any way connected. However, in this case the idea of virtual self is fairly consistent with some Buddhist ideas about selfhood. It is also consistent with the idea that one can, through concentration exercises and reflection, substantially and permanently alter one's perspective on the world of experience to the extent that one no longer relates to it via a sense of self. If the sense of self were wholly immaterial (a ghost in the shell) or material (i.e. "hardwired"), then meditation could have no effect on it; we could not rid ourselves of the sense of being a self through meditation and introspection if self were anything other than a simulation whose parameters we can tweak through how we think.


Morality and Continuity

In 2014 Thomas Metzinger wrote:
"As a philosopher, my conceptual point is that only if an organism simulates itself as being one and the same across time will it be able to represent reward events or the achievement of goals as a fulfillment of its own goals, as happening to the same entity. I like to call this the "Principle of Virtual Identity Formation": Many higher forms of intelligence and adaptive behavior, including risk management, moral cognition and cooperative social behavior, functionally presuppose a self-model that portrays the organism as a single entity that endures over time."
Here Metzinger has put his finger on the crucial point about living things. Living things act in ways that over time seem purposeful. We move towards goals and to some extent towards meta-goals. I'm wary of a teleological argument here. I mean, for example, that we seek out and consume food as a goal. And in anticipation of this we plant crops many months ahead of their ripening, and then store the resulting food, anticipating future need as a meta-goal. I don't mean, for example, that evolution is developing towards a general goal or anything of that nature. Desire, seeking behvaiour, and reward for fulfilling the desire have to be coordinated at some level. If they were not then we would have real difficulty with basic functions like eating and mating.

But crucially moral behaviour requires us to believe that we endure over time. Buddhist teaching on morality openly acknowledges this. The Jātaka stories are all about connecting actions to consequences over time, linking previous lives to present one. Buddhist metaphysics goes out the window at this point, because they disrupt the kind of continuity required for moral behaviour by weakening the links between behaviour in this life and reward in the next (I'll return to this point below). 

If I believe that I will not be the one to achieve the goal, that it will for example only be achieved by my grandchildren, then I am probably less motivated than if I could see an immediate benefit to myself. The classic example of this is the problem of climate change. Even where climate change is admitted to be caused by human activity, the political will to make the necessary changes is lacking, partly because the time scale over which the changes occur are too long for most people's imaginations, i.e. the not only go beyond the electoral cycle, but beyond an individual human life. Almost no one is willing to commit to spending resources on a project that has almost no immediate benefits, but which will make life easier in future centuries. And as frustrating as this is, it can hardly be surprising. We surely know enough about human motivation not to be surprised by this fact.

George Lakoff has described morality as a kind of book keeping exercise (see Moral Metaphors, 8 Nov 2013). Actions create mutual obligations for ourselves and those we have contact with, which may be conceived of as debts. As social animals we are always in debt to our social group, and need to keep track of the debts of the group as a whole. If, for example, food is shared with us a quid pro quo is expected that we might repay in kind or through something of equal value. A social group is held together by a network of these mutual obligations. Where I grew up, people are quite relaxed about taking on social obligations - we make friends easily. In England most people are at pains to avoid any new social obligations, so it's difficult to make friends. English people don't want to be in debt to strangers, though ironically they have amongst the highest levels of financial indebtedness in the world.

Different political ideologies evolve out of the different responses to these debts. In the present political climate of the UK we have a government which on has staked everything on paying back existing national debts (despite 0% interest rates) and not accruing any more debts (which by its own standards it is failing to do). We have an opposition which is confused about how to respond. The Brits are largely a conservative nation and don't like to see the government getting into debt. On the other hand household debt is very high and rising.

What most cultures do is extrapolate from this social model of fairness within the group and propose the idea that the world is fair. This is called the Just World Hypothesis. I've written about this in connection with the afterlife. Since life is patently not fair or just, the afterlife becomes the place of debt settlement. And an afterlife requires a matter/spirit duality to enable something to survive the death of the body. In afterlife theories in which the afterlife destination is determined by morality, the deeds of the deceased are weighed against the law. In the case of ancient Egyptian myth, as recorded in their Book of the Dead, the heart of the dead person is on one side of the balance and an ostrich feather representing the law is on the other. In some religions God does the judging. Being judged is a distinct milestone on the journey to the afterlife in all moralistic religions.

Buddhists tried to skirt this inherent eternalism by proposing that rebirth was governed by the same principle as the arising of vedanā, i.e. that the dying being was a condition for the next living being. But they almost immediate split into factions, each of which developed a different explanation for how this might happen. There was no consensus amongst Buddhists on how rebirth occurred or what it entailed. And no existing explanation survives its encounter with modernity (See The Logic of Karma16 Jan 2015). This is because trying to explain the afterlife by generalising a theory of how mental events are related doesn't work. It reduces the connection between actions and consequences. Hence, historically, Buddhists had to sustain two distinct discourses: one with respect morality (summed up as actions have consequences for me) and another for metaphysics (it is not me, but not another either). But in moral terms, as Buddhists tacitly admit, if it is not me that is game over for morality. The second part of the formula, not another, is not important because it is not me. Hence Buddhists both deny that it is you (or another); and at the same time emphasise that it really is you. Getting Buddhists, or even supposedly neutral scholars of Buddhism, to even admit that this duality exists has proved very difficult. One meets incredible resistance and even hostility to the very idea. Even though it is plain as day.

Morality, especially Buddhism morality, depends on being aware of and sensitive to the consequences of actions, but, as I say, our metaphysics creates a barrier to owning consequences. The metaphysics is so problematic that Nāgārjuna ends up repudiating the very idea of karma (or a being who does karma) as fictions of "relative truth". He describes them as illusions "like the cities of Gandharvas in the sky" (see Chapter 17 of Mūlamadhyamaka Kārikā). Connecting consequences to actions without invoking eternalism is almost impossible. The early Buddhists simply set aside metaphysics when it came to morality. They set aside the limitations of the anātman doctrine and taught that we are the owners of our karma, the heirs to our karma (Cf. Five Facts to Continuously Reflect On).

But if morality is a book keeping exercise and accounts are settled in the afterlife, then where are the books? Something has to provide a memory of our accounts that persists after death. For those worldviews that include a soul or an overseer god this is not a problem. Admitting supernatural entities solves the problem. Buddhists came up with various schemes to allow karma to accumulate and transfer. Highlighting the arguments that each came up with for the other views is a theme of my writing on karma. No Buddhist idea of how karma and rebirth work was universally accepted. Most sects thought that other sects had got the problem disastrously wrong. 

Morality depends on some connection between the person who acts and the person who suffers the consequence. And in those Just World worldviews in which justice is delivered postmortem, that connection must survive death. And this is precisely where Buddhist metaphysics of no-self are problematic. There are two main problems as I see it.
1. The relation of conditional arising is not sufficient to motivate anyone to act well. I argue that this is born out by Buddhist's own approach to teaching morality. I have already identified a dichotomy between metaphysical and moral teachings.
2. The flat denial of any self in many Buddhist metaphysical narratives, even an experiential self, undermines any possibility of morality. Also if there is actually no self, then everyone would be severely autistic and unable to respond to anyone else.
Hence the talk of no-self literally meaning there is no self must be at least partly wrong. Because even those people who claim to have broken the fetter of self-view (sakkāyadiṭṭhisaṃyojana) are still able to interact with people, to recognise them and respond appropriately to them. On the other hand any self we do have at the experiential level can only be a simulation created by our brain to help us navigate the world. The trouble is that existence and non-existent are black and white extremes when we need something a little more subtle. If instead the self is part of a virtual simulation then terms like existence and non-existence don't apply. If we abandon the attempt to prove this kind of all-or-nothing proposition one way or the other and view the self as a simulation then we can start asking more interesting questions. How does the brain achieve the kind of continuity required for goal seeking behaviour and thus for morality? Is it simply memory, or is there a more specific mechanism?

Earlier I mentioned the semantic problems of talking about self. Everyone understands something different by the relevant words. I have written about on several occasions the confusion of terminology. On one hand the meaning of ātman in Buddhist circles apparently changes depending on when and where it is being used. Initially the instruction seems to be that because ātman is a permanent unchanging entity it cannot be associated with any of the sense spheres. Thus, it cannot be experienced. And ipso facto cannot be known. There is a strict epistemological limit (despite what Vedantins may say). A permanent entity could not give rise to an experience. Nāgārjuna discusses this: we either always know about a permanent entity (past, present and future); or we never know. There can only be absolute knowledge or absolute ignorance of permanent entities; there can be no middle ground, no change from ignorance to knowledge. So ātman can never appear in experience (and nor can God). This is explicitly ruling out some unnamed extra sense beyond the five physical senses and the mind. There is no possibility of knowing by extra-sensory perception. And yet the same texts clearly believe in what we would call extra-sensory perception: that space is no impediment to knowledge. One can see things that are invisible, hearing things that are inaudible, and so on. That said the knowledge that comes this way is just an extension of sensory knowledge. One might see or hear at a distance, but no new senses are operating.

There is considerable confusion over how to translate ātman: soul, self, Self, ego, Ego, and so on. And on how to understand what it means at different times and in different contexts. As far as the Pāḷi texts are concerned they appear to be responding to the metaphysical entity as described by the Upaniṣads (see Gombrich 2009). There the ātman is a permanent unchanging entity that resides in our body, usually in our heart, and is not affected by the changes that our bodies and minds experience; not affected by life or death or suffering. Ātman is always pure and unadulterated. This is not what ego means, nor "self" in the usual sense. It does not equate to an homunculus either.



Morality in the Absence of Self

In discussing this issue with a colleague a resolution to this apparent conflict between karma and anātman emerged. In his view the sense of being a separate self is the origin of unskilful actions. While one has a sense of being a separate self, one will react to experience with attraction or aversion and thus create karma. So for someone with a simulated sense of self (i.e. all "normal" human beings), it is necessary for them to believe that they will suffer the consequences of their actions in order to motivate them to be moral. However, when one eradicates the sense of being a separate self, this also removes the motivation to act unskilfully. Greed and hatred are responses of the self to opportunities and threats in the environment. No self means no greed, no acquisitiveness; no hatred, no aversion. Thus the need to motivate the person to be ethical through the fear of consequences is also eliminated at the same time. 

Part of the problem we have in understanding this and communicating it, is that the few people who attain this state of spontaneous morality have not yet been properly studied. Worse we still rely on Iron Age or Medieval worldviews that are rooted in profoundly wrong conceptions of the world, life, and people. As yet we have no good way of integrating this perspective into a modern body of knowledge. The beginnings of a way forward may emerge from the work of people like Andrew Newberg who is studying the neuroscience of religious experiences. He calls his field "neurotheology" and is particularly interested in theistic interpretations of religious experiences, but has also studied the brains of Buddhist meditators. Ideally we would have a cohort of people who experience themselves as having a self who could participate in a baseline study before they practised and then again once they had eliminated the sense of self. This would give us a much better understanding of what has happened to them.

It would be especially interesting to see if anything changes in the way that they parse grammar. It is common for such people to use pronouns in the conventional way, but to say that they no longer understand the world to be divided up into I, you or they. So how they use pronouns accurately becomes an interesting question.

Unfortunately all we have to go on at present is the testimony of those who experience the cessation of the sense of being a separate self and they are themselves a source of confusion. It's clear that many approaches to achieving this state exist and that people from different traditions are attaining it. But each of them seems to see in it the culmination of their particular tradition and explain that their traditional interpretation of the experience is the correct one. As David Chapman recently observed:
"People in non-ordinary states, produced by psychedelic drugs or meditation, often proclaim sudden, unshakable, universal understanding. They rarely or never can explain their supposed understanding. I think these are probably mostly illusory. Such experiences may give genuine but ineffable insight into some things. I’m reasonably sure they involve no actual understanding of most things." - The Illusion of Understanding
This is also my conclusion from trying to correspond with a few people who talk about being permanently in a non-ordinary state, and many in-depth conversations with a friend who spends a good deal of his time in non-ordinary meditative states. 

Compare the conclusions of Gary Webber for example. For him the dropping away of ego is the confirmation of the teachings of Ramana Maharshi, an early 20th Century teacher of Advaita Vedanta. Webber understands his experience in Vedantin terms and is critical of the Buddhist teaching of emptiness. Though he clearly doesn't really understand the emptiness teachings. For Webber, for example, free will is an illusion because in his view everything ties back to an unchanging essence that underlies the universe. This combines ideas from the Upaniṣads with the influential Sāṃkhyā school of Indian metaphysics (a huge influence on Patañjali and Yoga metaphysics). For Webber this kind of metaphysical speculation is underpinned by his experience of awakening. But Buddhists who describe more or less the same experience -- i.e. the loss of internal dialogue and a first person perspective -- argue that no such metaphysical speculation is valid. The Awakened can still disagree amongst themselves on metaphysics (as they have traditionally done throughout history, especially in India).

This discrepancy plays out in other ways and one that particularly interests me is the use of language, particularly pronouns and grammatical agents. People with no self say that they experience no first-person point of view, that they do not see the world in terms of self and other. And yet they are still able to accurately use pronouns. If there truly was no distinction at all between self and other, then pronouns would be confusing. If there were genuinely no reference point in experience, then one would struggle to accurately ascribe actions or qualities to agents. A pronoun is used to point out the agent of an action or owner of a property. So the awakened still have access to the knowledge of how pronouns map onto situations, on how verbs require agents, and thus on some level are able to distinguish agents. Mind you most of us use pronouns without thinking, so perhaps it is unfair to expect the awakened to have insight into this issue. Until we better understand how anyone with no first-person perspective can use pronouns accurately we have to remain suspicious of the generalisations that those people draw from their experience. Something does not add up.

In other words the awakened still seem to be unable to look past their own subjectivity. That subjectivity may be radically different from mine, but it still seems to have the same kinds of limitations. Logical fallacies and biases are still in play. What we need is for a few people who have experienced enlightenment to become lab rats, so that we can study them. We need to better understand the nature of the changes they have experienced in order to better codify them and make them available to other people, if in fact that is desirable.

~~oOo~~


Metzinger, Thomas (2014). What Scientific Idea Is Ready For Retirement? The Edge. https://edge.org/response-detail/25446

Related Posts with Thumbnails