Human as animal
Locke allows the imagery of animals in nature to shape his argument about humans in various portions of the Essay. This means remembering the aspects of human life and consciousness that are plainly animal in nature. For instance, humans eat and experience hunger, which they share with animals. Their urge to rank high in the social hierarchy and to reproduce sexually are also aspects of life that are technically shared with other mammals. This imagery is in contrast with other considerations about human nature.
Humans as mysteriously different
Locke doesn't just say that humans are the same as animals. Instead, he qualifies that humans are indeed animals with instincts, but then he goes further to show that humans are actually more than their animal counterparts. Humans can use language, so that the field of linguistic information is also within the human nature. This, alongside various other aspects, like the ability to fathom the future and the power to create art and technology, separates humans from animals, but how does it do that, and why? That is the question of these writings.
Philosophy
The speculative nature of philosophy is described through imagery. Instead of seeing philosophy as a self-explanatory phenomenon, Locke depicts philosophy as an aspect of human nature, because humans by nature are inquisitive and curious. This is in addition to their animal nature, because philosophy is a categorization of linguistic data as well as a treatment of physical reality. He is clearly attempting to side step the previous philosophy of his time to offer some new insight.
Science
Through philosophical considerations, Locke arrives at the unique nature of the scientific method. By analyzing reality with cold detachment and rigorous testing, Locke sees that humans could begin to understand a new more literal truth, instead of merely categorizing the aspects of the human imagination or of the human mind. For instance, science sees the apple for its myriad functions and facts, whereas human consciousness sees "food."
