Since every thing that bears the character of reflection cannot be primitive, and supposes an anterior state, it follows, that the principles which are the subject of our study could not have possessed at first the reflective and abstract character with which they are now marked, that they must have shown themselves at their origin in some particular circumstance, under a concrete and determinate form, and that in time they were disengaged from this form, in order to be invested with their actual, abstract, and universal form. These are the two ends of the chain; it remains for us to seek how the human mind has been from one to the other, from the primitive state to the actual state, from the concrete state to the abstract state. How can we go from the concrete to the abstract? Evidently by that well-known operation which is called abstraction. Thus far, nothing is more simple. But it is necessary to discriminate between two sorts of abstractions. In presence of several particular objects, you omit the characters which distinguish them, and separately consider a character which is common to them all--you abstract this character. Examine the nature and conditions of this abstraction; it proceeds by means of comparison, and it is founded on a certain number of particular and different cases. Take an example: examine how we form the abstract and general idea of color. Place before my eyes for the first time a white object. Can I here at the first step immediately arrive at a general idea of color? Can I at first place on one side the whiteness, and on the other side the color? Analyze what passes within you. You experience a sensation of whiteness. Omit the individuality of this sensation, and you wholly destroy it; you cannot neglect the whiteness, and preserve or abstract the color; for, a single color being given, which is a white color, if you take away that, there remains to you absolutely nothing in regard to color. Let a blue object succeed this white object, then a red object, etc.; having sensations differing from each other, you can neglect their differences, and only consider what they have in common, that they are sensations of sight, that is to say, colors, and you thus obtain the abstract and general idea of color. Take another example: if you had never smelled but a single flower, the violet, for instance, would you have had the idea of odor in general? No. The odor of the violet would be for you the only odor, beyond which you would not seek, you could not even imagine another. But if to the odor of the violet is added that of the rose, and other different odors, in a greater or less number, provided there be several, and a comparison be possible, and consequently, knowledge of their differences and their resemblances, then you will be able to form the general idea of odor. What is there in common between the odor of one flower and that of another flower, except that they have been