Mankind
Unsurprisingly, we find that humankind is a major character in Locke's Essay, especially the unique qualities of a human being in contrast with animals. The question of Book I is plainly rooted in this discussion, deliberating whether humans have essentially given beliefs and mental capabilities, or whether the mechanisms of society merely produce a similar output. The mystery of man's mind is on full display in these chapters.
The scientist
The scientist is someone who takes on the additional role of understanding life objectively. This means stepping outside of commonly held beliefs to understand life from a different point of view. This is inherently challenging, but through the processes of reason, a scientist could begin to understand life in new ways. Locke says these discoveries will be contrary to popular belief by definition, and he calls for scientific reason in the schools of philosophy.
The human animal
In Book II, there is a slight modulation about human nature. Instead of focusing on the mind, potential, and linguistic powers of humans, Locke looks to the human as an animal. He says that animal nature is clearly evident in our perception of reality. An apple is "food" to a human, which is an animal instinct. He seeks to distinguish which aspects of Human Understanding are simply human animal instincts being perceived, and which are truly different than animal instincts.
