II. The constitution of human creatures, and indeed of all creatures which come under our notice, is such, as that they are capable of naturally becoming qualified for states of life, for which they were once wholly unqualified. In imagination we may indeed conceive of creatures, incapable of having any of their faculties naturally enlarged, or as being unable naturally to acquire any new qualifications. But the faculties of every species known to us, are made for enlargement; for acquirements of experience and habits. We find ourselves, in particular, endued with capacities, not only of perceiving ideas, and of knowledge or perceiving truth, but also of storing up ideas and knowledge by memory. We are capable, not only of acting, and of having different momentary impressions made upon us; but of getting a new facility in any kind of action, and of settled alterations in our temper or character. The power of the two last is the power of habits. But neither the perception of ideas, nor knowledge of any sort, are habits; though absolutely necessary to the forming of them. However, apprehension, reason, memory, which are the capacities of acquiring knowledge, are greatly improved by exercise. Whether the word habit is applicable to all these improvements, and in particular how far the powers of memory and of habits may be powers of the same nature, I shall not inquire. But that perceptions come into our minds readily and of course, by means of their having been there before, seems a thing of the same sort, as readiness in any particular kind of action, proceeding from being accustomed to it. Aptness to recollect practical observations, of service in our conduct, is plainly habit in many cases. There are habits of perception, and habits of action. An instance of the former, is our constant and even involuntary readiness, in correcting the impressions of our sight concerning magnitudes and distances, so as to substitute judgment in the room of sensation, imperceptibly to ourselves. It seems as if all other associations of ideas not naturally connected, might be called passive habits; as properly as our readiness in understanding languages upon sight, or hearing of words. Our readiness in speaking and writing them, are instances of active habits.