There are two principal forms of common sense which it is desirable clearly to distinguish. The first is what the philosopher means by common sense, when he attributes to it the formation of those original convictions or ultimate beliefs, which cannot be resolved into simpler elements, and which are accepted by every normally constituted human being as direct cognitions of his own mental states. It might, indeed, be maintained that this necessary acceptance of propositions which only need to be intelligibly stated to command unhesitating and universal assent, cannot rightly be termed an act of judgment. But just as sense-perceptions, which are intuitive in the lower animals, have been acquired in man by a process of self-education in the earliest stages, in which acts of judgment are continually called for, so may we regard the autocratic deliverances of the universal common sense of mankind as really having, in the first instance, the characters of true judgments, each expressing the general resultant of uniform experience,--which may be partly of the individual, and partly that of the race embodied in the constitution of each member of it. The second or popular acceptance of the term common sense, on the other hand, is that of an attribute which judges of things whose self-evidence is not equally apparent to every individual, but presents itself to different individuals in very different degrees, according in part to the original constitution of each, and in part to the range of his experience and degree in which he has profited by it. This is the form of common sense by which we are mainly guided in the ordinary affairs of life: but inasmuch as we no longer find its deliverances in uniform accordance, but encounter continual divergences of judgment as to what things are self-evident,--some being so to A whilst they are not so to B, and others being self-evident to B which are not so to A,--it cannot be trusted as an autocratic or infallible authority. And yet, as Dr. Reid truly says, "disputes very often terminate in an appeal to common sense;" this being especially the case, when to doubt its judgment would be ridiculous. If the view here taken be correct, these two forms--which may be designated respectively as elementary and as ordinary common sense--have fundamentally the same basis; and we may further connect with them as having a similar genesis, those special forms of common sense, which are the attributes of such as have applied themselves in a scientific spirit to any particular course of inquiry,--things coming to be perfectly self-evident to men of such special culture, which ordinary men, or men whose special culture has lain in a different direction, do not apprehend as such.