Progress in thinking is measured by progress in discrimination. The skilled thinker divides the large unit into very small units, compares these with each other and then reunites them into a more perfect and unified whole. First there is an analysis and then a synthesis. Like a shuttle the power of thought works in and out; it goes in to separate, it comes out to unify.
There is another aspect in the analogy between the life of the physical and mental worlds. Somewhere in the order of progress there is a connecting link between the mineral and vegetable kingdoms, likewise between the vegetable and animal kingdoms. The sensation is as much a state of feeling as an act of knowing and consequently is the connecting link between the _feeling_ mind and the _knowing_ mind. If the percept is the result of thinking as well as intuition then it may stand for the dividing line between the _knowing_[4] mind and the _thinking_ mind.
_Conception is the process of thinking many notions into one class._ The product of such a process is called a concept. (1) The concept may stand for a group of concrete _general_ notions――as the concept _man_, which stands for the five general notions: Caucasian, Mongolian, Ethiopian, Malay and American Indian. (2) The concept may stand for a group of concrete _individual_ notions. For example, the same concept _man_ represents all of the individual men of the world. (3) The concept may stand for a group of _abstract general_ notions. To wit: Virtue represents such general notions as honesty, justice, industry, purity, etc. (These are general notions because they admit of a subdivision into kinds. Industry, for instance, may be divided into two kinds: mental industry and physical industry.) (4) The concept may stand for a group of _abstract individual_ notions. To illustrate: Blueness stands for the various shades of blue, as sky blue, bird’s egg blue, navy blue, etc.
Thus does the concept stand for a group of all kinds of notions, individual and general, abstract and concrete.
I see for the first time in my life a pencil. In other words I become conscious of a localized group of sensations――this is a percept. I am told that the name of that which I see is _pencil_. I note that this particular pencil has a thread of black lead encased in a cylindrical strip of wood which is brown in color. A second object is presented which I recognize as a pencil though the shape is prismatic rather than cylindrical and the color green rather than brown. But I call it a pencil because it has a thread of black lead encased in a strip of wood. The notion which I now have in mind stands for two pencils and is therefore represented by a class name. As I observe other pencils of various shapes, made of wood and paper with threads of different colored lead, my notion of pencil broadens till finally it stands for all pencils. This is the process of conception according to the definition, namely: “The process of thinking many notions into one class.” In this case the notions are individual.