The author of this chapter is essentially trying to find the relationship of the individual to the world around him. He wants to discover, define and clarify how the individual interrelates with the external world, the effects it has on him, and the inherent realities of that world and himself. The author seeks to discover the content and meaning of sensation, ideas, and understanding with reference to this relationship between the world and the individual.He seeks to disentangle these concepts and realities which we generally confuse and juxtapose with one another.
In trying to make these distinctions, the author first author clarifies what he means by ideas (what the mind perceives in itself), qualities (those elements in an object which gives it the power to produce ideas in our minds), primary qualities (those elements of an object which are constant and permanent and a part of the object itself), secondary qualities (those elements which are not truly parts of the object themselves but which produce in us the sensation or perception of color, sound, taste, etc.) (134-135).
Then the author asks the question, "Why is Whiteness and Coldness in Snow, and Pain not, when it produces the one and the other Idea in us, and can do neither, but by the Bulk, Figure, Number, and Motion of its solid Parts?" (137). In other words, the author wants to find out the nature and course of the process whereby we experience and comprehend the objects of the world, and what elements of these objects and of ourselves (idea, sensation, understanding) are actually parts of the objects or of ourselves.
Focusing on the subject of snow, the author first argues, quite reasonable, that the bulk, figure and motion of snow "are really in them, whether any one's Senses perceive them or no: and therefore they may be called real Qualities, because they really exist" in snow. However, "Light, Heat, Whiteness, or Coldness, are no more really in them, than...