Fascinating topic.
In Buddhist philosophy, consciousness (Pali: viññāṇa, Sanskrit: vijñāna) is merely a causally conditioned phenomenon that helps constitute the human personality despite having no relation to a permanent identity or self as an agent. With regard to mind and consciousness in particular, a unique metaphor is used by the Buddha to describe their transient nature:
Just as a monkey, swinging through a forest wilderness, grabs a branch. Letting go of it, it grabs another branch. Letting go of that, it grabs another one. Letting go of that, it grabs another one. In the same way, what's called 'mind,' 'intellect,' or 'consciousness' by day and by night arises as one thing and ceases as another.
Assutava Sutta, SN 12.61
Evidently, one cannot find a mind, consciousness, or self that is separate from change. There is no true self, only the sense of self that arises and ceases at each passing moment, never the same from one instant to the next.
Nonetheless, it is tempting to identify with consciousness, which seems to animate a being, thus giving it life. This tendency to identify with consciousness, along with the other aggregates, is acknowledged as a form of clinging, which is ultimately harmful.
An underlying theme of Buddhist philosophy is the interdependent nature of phenomena, expressed in terms of dependent co-arising (Pali: paticca samuppāda; Sanskrit: pratītya samutpāda).
"And what is dependent co-arising? From ignorance as a requisite condition come fabrications. From fabrications as a requisite condition comes consciousness. From consciousness as a requisite condition comes name-&-form. From name-&-form as a requisite condition come the six sense media. From the six sense media as a requisite condition comes contact. From contact as a requisite condition comes feeling. From feeling as a requisite condition comes craving. From craving as a requisite condition comes clinging/sustenance. From clinging/sustenance as a requisite condition comes becoming. From becoming as a requisite condition comes birth. From birth as a requisite condition, then aging & death, sorrow, lamentation, pain, distress, & despair come into play. Such is the origination of this entire mass of stress & suffering.
Paticca-samuppada-vibhanga Sutta, SN 12.2
Dependent co-arising thus facilitates a deeper understanding of not-self by demonstrating that the emergent sense of self necessarily depends on other factors outside the alleged boundaries of a person:
When a disciple of the noble ones has seen well with right discernment this dependent co-arising and these dependently co-arisen phenomena as they are actually present, it is not possible that he would run after the past, thinking, 'Was I in the past? Was I not in the past? What was I in the past? How was I in the past? Having been what, what was I in the past?'
Paccaya Sutta, SN 12.20
In the sequence of dependently co-arisen links, consciousness has no inherent existence. It is troublesome to even refer to dependent origination as a sequence or its individual components as links due to the inter-dependent, bi-directional, co-arising of phenomena. As each link (Pali, Sanskrit: nidana) is relative and interconnected, dependent co-arising is not a linear chain. Due to the non-linearity of dependent co-arising, the sequence of conditioning is anything but unidirectional. The mutually conditioned relationship between name-&-form on one hand and consciousness on the other is illustrated by the following passage:
I will give you an analogy; for there are cases where it is through the use of an analogy that intelligent people can understand the meaning of what is being said. It is as if two sheaves of reeds were to stand leaning against one another. In the same way, from name-&-form as a requisite condition comes consciousness, from consciousness as a requisite condition comes name-&-form.
Nalakalapiyo Sutta, SN 12.67
Name-&-form and consciousness are thus shown to be mutually dependent. Without one, the other could not exist. This point is reiterated on multiple occasions:
'Name-&-form exists when consciousness exists. From consciousness as a requisite condition comes name-&-form.' [...]'Consciousness exists when name-&-form exists. From name-&-form as a requisite condition comes consciousness.' [...] 'Name-&-form doesn't exist when consciousness doesn't exist. From the cessation of consciousness comes the cessation of name-&-form.' [...] 'Consciousness doesn't exist when name-&-form doesn't exist. From the cessation of name-&-form comes the cessation of consciousness.'
Nagara Sutta, SN 12.65
Clearly, consciousness is not an isolated link within dependent co-arising, but part of an interdependently arisen stream that is mistaken as a substance, supporting the illusion of self.
Not only are mind and body mutually constitutive, but mentality-&-materiality, in the singular, is inseparable from consciousness. In other words, consciousness cannot be surgically extracted from mentality-&-materiality to exist on its own. This is further illustrated in the following discourse:
Were someone to say, 'I will describe a coming, a going, a passing away, an arising, a growth, an increase or a proliferation of consciousness apart from form, from feeling, from perception, from fabrications,' that would be impossible.
Upaya Sutta SN 22.53
In Buddhism, consciousness is not its own entity, separable from material existence (which constitute form), or from sensations, perceptions, and cognition (which mutually constitute name). There is a clear qualitative difference between name (the mental) on one hand, and form (the physical) on the other, yet the Buddha always teaches that they are mutually dependent (see again the Upaya Sutta, SN 22.53; Nagara Sutta, SN 12.65; Nalakalapiyo Sutta, SN 12.67; etc.).
Interestingly, the place of consciousness in the chain of dependent origination is immediately succeeding mental fabrications and immediately preceding name-&-form, coming between cognition on one side and mind and matter on the other. On the basis of dependent co-arising, fabrications condition consciousness and consciousness conditions name-&-form, which may appear counter-intuitive. Only upon a clarification of definitions does the order of these conditional relationships make sense:
"And what is name-&-form? Feeling, perception, intention, contact, & attention: This is called name. The four great elements, and the form dependent on the four great elements: This is called form. This name & this form are called name-&-form.
"And what is consciousness? These six are classes of consciousness: eye-consciousness, ear-consciousness, nose-consciousness, tongue-consciousness, body-consciousness, intellect-consciousness. This is called consciousness.
"And what are fabrications? These three are fabrications: bodily fabrications, verbal fabrications, mental fabrications. These are called fabrications.
Paticca-samuppada-vibhanga Sutta, SN 12.2
Fabrications of body, mind, and speech give rise to sense consciousness, and sense consciousness conditions the ability to perceive, attend, and so on. In Buddhist philosophy, the nature of ones consciousness depends on the nature of ones fabrications (otherwise understood as dispositions) and consciousness in turn factors into the nature of name-&-form, the psychophysical personality. Thus, consciousness cannot exist in-and-of-itself, a point reiterated in the scriptures:
It's good, monks, that you understand the Dhamma taught by me in this way, for in many ways I have said of dependently co-arisen consciousness: 'Apart from a requisite condition, there is no coming-into-play of consciousness.'
Mahatanhasankhaya Sutta, MN 38
Ultimately, consciousness is not an isolated link within the chain of dependent co-arising, but part of the interdependent reality of phenomena. Because consciousness is inter-dependently co-arisen, it cannot be claimed to be in any way distinct from the things that give rise to it.