It is to the phenomena only, then, that our attention is to be given, not to any vain inquiries into the absolute nature of the substances which exhibit the phenomena. This alone is legitimate philosophy,--philosophy which must forever retain its claim to our assent, amid the rise and fall of all those spurious speculations, to which our vanity is so fond of giving the names of _theory_ and _system_. Whatever that may be, in itself, which feels, and thinks, and wills,--if our feelings, and thoughts, and volitions be the same--all which we can know, and compare, and arrange, must be the same; and, while we confine our attention to these, the general laws of their succession which we infer, and the various relations which they seem to bear to each other, may be admitted equally by those whose opinions, as to the absolute nature of the feeling and thinking principle, differ fundamentally. It requires no peculiar supposition, or belief, as to the nature of the mind, to know, that its trains of thought are influenced, by former habits, or casual association; and every fact, which the immaterialist has accurately observed and arranged, with respect to the influence of habit or association, may thus, with equal reason, form a part of the intellectual and moral creed of the materialist also. On these two systems it is not at present my intention to make any remarks; all which I wish, now, is to explain to you, how independent the real philosophy of the mind is, of any fanciful conjectures, which may be formed, with respect to its essence. It differs from these, as Mr. Stewart has well observed, in the same manner “as the inquiries of Galileo, concerning the laws of moving bodies, differ from the disputes of the ancient Sophists, concerning the existence and the nature of motion,” or as the conclusions of Newton, with respect to the law of gravitation, differ from his query concerning the mode in which he supposed that gravity might possibly be produced. The hypothesis, involved in the query, you may admit or reject; the conclusions, with respect to the law of gravitation itself, as far as relates to our planetary system, are, I may say, almost beyond your power of rejecting. The philosophy of mind then, and the philosophy of matter, agree, in this respect, that our knowledge is, in both, confined to the mere phenomena. They agree also, in the two species of inquiry which they admit. The phenomena of _mind_, in the same manner as we have seen in the case of _matter_, may be considered as complex and susceptible of analysis, or they may be considered as successive in a certain _order_, and bearing, therefore, to each other the reciprocal relation of causes and effects.