The mind–body problem is a philosophical problem concerning the relationship between thought and consciousness in the human mind, and the body. The issue is this. Though it is obvious that mental events and physical events are somehow related, it is not obvious what the nature of this relation is. For example, it is obvious that feelings of sadness (which are mental events) will cause people to cry (which is a physical state of the body), or that finding a joke funny (a mental event) will cause one to laugh (another bodily state), or that feelings of pain (in the mind) will cause avoidance behaviours (in the body), and so on. Similarly, it is well known that changing the chemistry of the body (and the brain especially) via drugs (such as antipsychotics, SSRIs, or alcohol) can change one's state of mind in nontrivial ways. Or, in the other direction, it is known that therapeutic interventions like cognitive behavioural therapy will change cognition in ways that have downstream effects on the bodily health. These are only a few examples of the numerous ways in which the state of the mind and body seem to be intimately tied; many more examples can be found simply by reflecting on one's day-to-day experiences. In general, the existence of these mind–body connections seems unproblematic. Issues arise, however, once one considers what exactly we should make of these relations from a metaphysical or scientific perspective. Such reflections quickly raise a number of questions like: Are the mind and body two distinct entities, or a single entity? If the mind and body are two distinct entities, do the two of them causally interact? Is it possible for these two distinct entities to causally interact? What is the nature of this interaction? Can this interaction ever be an object of empirical study? If the mind and body are a single entity, then are mental events explicable in terms of physical events, or vice versa? Is the relation between mental and physical events something that arises de novo at a certain point in development? And so on.