Kiṃ nu sattoti paccesi, māra diṭṭhigataṃ nu te;
Suddhasaṅkhārapuñjoyaṃ, nayidha sattupalabbhati.
Yathā hi aṅgasambhārā, hoti saddo ratho iti;
Evaṃ khandhesu santesu, hoti sattoti sammuti.
Dukkhameva hi sambhoti, dukkhaṃ tiṭṭhati veti ca;
Nāññatra dukkhā sambhoti, nāññaṃ dukkhā nirujjhatī’’ti
Māra was disappointed at not frightening Vajirā, and he disappeared. This is the famous simile of the chariot from the Vajirā Sutta, in the Saṃyutta Nikāya (5:10; PTS S i.136). It is used to illustrate the idea that we are only an assemblage of parts, that nothing really exists in the absolute sense - as the sutta says when the parts come together we conventionally say 'a being'. This collection of parts is also called a mere heap of fabrication (suddha-saṅkhāra-puñjoyaṃ). But what are these parts? They are the khandhas. Traditionally these are defined as that which conventionally makes up a being. The definition is circular: a being is made up of the things that make up a being. There's not much information in that interpretation. However Sue Hamilton has given us a better way of thinking about the khandhas: they are the apparatus of experience. That is, instead of thinking of the khandhas as what makes up a being, we can think of the khandhas as the minimal requirements for having an experience. Briefly we have the locus of experience (form/rūpa), then "having met with sensory data (vedanā) [via the physical sense organs] we process it: we become aware of and identify the sensation (saññā), we categorise it and name it (viññāṇā), and we respond affectively to it (saṅhkāra)." [The Apparatus of Experience]
What makes you resort to belief in 'a being' Māra?
A heap of mere fabrication, a being is not found here.
Just as the combination of parts is called 'a chariot';
Thus while there are the apparatus of experience, conventionally there is 'a being'
For only suffering is produced; suffering persists, and ceases.
None other than suffering is produced, none other than suffering ceases.
To my mind the focus on experience explains why no being is found. What might be found is the experience of a being, but there is no being apart from experience. However note the third verse spoken by Vajirā. It says that it is only suffering that arises, persists and ceases. Only suffering. Without this part of the verse the received explanation works alright. But the third verse tells us something extra. Here is a confirmation that what arises in dependence on causes are experiences. In my essay on the first verse of the Dhammapada I said: "... if we fail to see and understand the nature of experience (yathābhūta-ñāṇadassana), then suffering follows, just as the wheel follows the ox which draws the cart". Dukkha in this view is all unenlightened experience. This sounds a bit miserable, but as I recently pointed out [proliferation] it's not that pleasure is bad, but that we mistake the pursuit of pleasant sensations as leading to happiness, which they do not.
This kind of sutta where Māra visits someone and tries to put doubts in their mind is quite common. Māra here seems to be a psychological metaphor, i.e. Māra represents our own doubts coming to the surface. The tactic of getting into dialogue with that doubting voice is something that is used by some psychologists. It also resembles the approach of Cognitive-Behavioural Therapy - identifying thoughts and deciding whether to take them seriously or ignore them.
So where the apparatus of experience come together we conventionally say there is a being. But this is to mistake the experience of being, for something more substantial. We need to focus on experience and on the processes by which we have experiences, because it is experience - especially suffering - that arises in dependence on conditions. It is our failure to recognise experiences in general and suffering in particular as dependent, that causes us to suffer.
While the idea of a 'being' as made up of parts and therefore insubstantial and impermanent is far from wrong, I think the use to which the verse is put shows the weakness of taking verses out of context. Because the real import, the central point of the simile, occurs in the third verse - only suffering arises - and this is routinely left out of presentations of the Dharma. Here the context reveals once again that whatever the truth of ontology and the reality of beings, the Buddha was focussed on the problem of suffering.
The chariot simile is from the Vajirā Sutta (S 5:10; S i.136) Pāli text from CSCD Pāli Tipiṭaka; pg 230 in Bhikkhu Bodhi's translation which is also available on Access to Insight; translated by Bikkhu Thanissaro on Access to Insight.
image: from Achaemenid Persia by Mark Drury. The picture is of a chariot from Afghanistan but would have been very similar to Indian war chariots.