Updated: Jan 22, 2020
We need psychoactives to circumvent the manifestation of behavioural evolutionary mismatches and the pain that they accrue on us. Our natural behavioural tendencies evolved in a hunter gatherer setting very different from the world in which we live. As a result, we are led by our instincts to behave in ways that are not conducive to our own success. This may be correctable with compounds.
For example: The lust for revenge is a human characteristic that once served to warn others not to try and harm the vengeful individual. Today revenge is counterproductive and is best ignored, but ignoring anger is difficult. It can be curbed by, meditation, medication or habit.
Another example, the tendency to be peckish. It used to be the case that food was not as abundant and accessible as it is today. Those who were peckish were constantly on the lookout for more food and consequently were better fed. Today this tendency causes obesity and substantially harms the individual that has inherited this behavioral trait if he has not overcome it.
These evolutionary mismatches cause no end of frustration and confusion as we struggle between what our logic tells us and what our heart feels. This internal conflict between what we know we should and what we feel we want is the cause of many of life's insecurities and lamentations. It is compounded by the biblical teachings of having been made in God's image and the resulting global feeling of entitlement to happiness and other worldly gifts.
But a practical theory of mind, once which measures performance at a task under the influence of different compounds could help us depart from our prehistoric heritage and behave according to the needs of our time.
Psychoactives also let us ponder consciousness. A single milligram of a small molecule compound contains hundreds of billions of molecules, each one of which can create an interaction with a receptor.