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tures, in a way the most necessary to their wants, and most interesting to their feelings. You will be enabled to confer that which sick kings would fondly purchase with their diadems; that which wealth cannot command, nor state nor rank bestow. You will be able to alleviate or remove disease, the most insupportable of human afflictions, and thereby give health, the most invaluable of human blessings.
I shall not, however, gentlemen, waste your time in expatiating on this topic, because you will feel much more than I can utter, and because all that can be said or thought of it, seems concentrated in one brief but enthusiastic sentence of Cicero, which therefore I quote. In nullare, propius ad deos homines accedunt, quam salutem hominibus dando.
In occupying the situation of the last gentleman who taught in this place, Sir Everard Home, who has pursued the path of science which Mr. Hunter pointed out, with a considerable talent for observation, and with a degree of zeal and industry, scarcely to be expected from one whose time and at- f tention have been otherwise so much engaged; I also, equally with him, feel interested in impressing on the minds of my audience, the advantages we have derived from the labours of Mr. Hunter, and from pursuing that mode of study and enquiry which he adopted, and inculcated: and I am desirous on the present occasion, to engage your attention in the consideration of the probability and rationality of his theory of life.
The term theory, in philosophical language, like hypothesis, denotes the most plausible and rational mode of accounting
for certain phaenomena, the causes of which have not been fully developed. In applying these terms to medical and physiological subjects, I may be allowed to define what I think they designate, and what I intend to convey by them. By the word theory I mean a rational explanation of the cause or connexion of an apparently full or sufficient series of facts: by hypothesis, a rational conjecture concerning subjects in which the
series of facts is obviously incomplete.
The formation of an hypothesis excites us to enquiries, which may either confirm or confute our conjectures; and which may, by enabling us to discover the deficient facts, convert our hypothesis into a theory. Believing the facts collected by the ingenuity and industry of Mr. Hunter, to be sufficient to establish his opinions respect
ing life, I havethereforecalled them, atheory. There was a time when medical men entertained so determined a dislike to the word theory, that they could scarcely tolerate the term. If any such remain, I would beg them to reflect that hypothesis and theory are the natural and inevi. table result of thinking; so that if they
refuse to allow of any theory, they must prohibit all thought.
The antipathy which some have entertained to the term theory, has arisen from its misapplication. For opinions drawn from very partial views of subjects, sometimes having no foundation on facts; opinions formed by processes of mind, similar to those which occur in dreaming, when lawless imagination produces combinations and associations without any reference to realities; opinions, as unlike what I should understand by theory as darkness is to light, have neverthelessbeen often proposed as theories and so denominated. That such foolish speculations, such awaking dreams, will mislead and deceive us, cannot be doubted ; and hence has arisen the prejudice which some
have entertained against the term.
The greatest philosophers were through the whole course of their enquiries and demonstrations, theorists. Theorizing, according to my conception of the word, means nothing more than thinking correctly, in a concatenated manner, and in conformity to rules which I shall presently have occasion to notice. It is scarcely necessary for me to assert that this kind of thinking is useful, and promotive of Science. For was it not thinking in this manner on the cause of an apple falling from a tree, that led Sir Isaac Newton to ascertain the laws of attraction? was it not thinking thus which led him