Life on Earth is an example of a system. Thus, through time, one might expect it to evolve (see previous chapter). The theory in a nut shell is that we have developed to form similar groups, defined by their shared characteristics (e.g. species). Within these groups there are slight variations (e.g. size, shape, location, etc.) which determine the likelihood of the survival of the genetic code of individual life forms. If certain attributes (e.g. having eyes) help the majority of individuals to pass on their genes, then these characteristics become common in general.
The theory of the evolution of life can go to explain why we think and feel as we do, that is to say, why we perceive existence as we do. It would clearly be important, when trying to find the truth, to consider how a mind that came into being by a process of evolution might perceive existence.
If the attributes that make up our minds have been passed down through countless generations then one can deduce that they have been evolutionary 'successful'. These attributes will dictate the thoughts that we are likely to have which, one way or another, previously aided the propagation of our ancestors' genetic code.
This propagation, however, does not require that these attributed tended to produce truthful or accurate representations of reality. It just requires that they tended to be beneficial in the environment in which they took place.
Notably the propagation of genetic material does not necessarily require happy or content states of mind.
It is possible therefore that we might inherit tendencies to think in ways that are not necessarily honest, or that do not necessarily make us happy. It would therefore be wise to make the acheivement of 'truthfulness' and 'contentment' conscious decision in our lives, instead of just assuming that they always come about naturally. In fact, by the very presence of discontentment and dishonesty we can deduce that these negative concepts are quite naturally and to avoid them must take a certain amount of effort, if it was easy and simple then everyone would be happy all the time. The 'best answer' to the question of how to be happy is not self-evident, although it will certainly involve applied efforts. Better to work at being happy then suffer in idleness.