of the facts on which it is based. We may therefore say that science consists of truths alone, but not of facts alone; and we have already seen that scientific truths include facts, ideas, and general truths. It should also be added that a fact has in itself no scientific value whatever. Its value consists entirely in the use we make of it, or the interpretation we give it. In other words, the mind alone gives it value. Proclus tells us the Epicureans used to say that eveji asses know the fact that any two sides of a triangle are together longer than the remaining one, and act accordingly; but they are not, therefore, acquainted with the science of geometry. Many classes of facts are acquired by the lower animals; but not being interpreted they fail to contribute to scientific ends. Pacts, then, have a mere "potential or subsequent value, and the only advantage of possessing them is the possibility of rising by a mental process to the idea, the principle, or the law which governs them;" or to the ideas in the Divine mind, which are shadowed forth by them. Facts are indeed the "body of science," as Dr. Samuel Brown remarks; but the "ideas " and conclusions they suggest "are its spirit" and its soul. And "our real knowledge," says a recent writer, "consists not in an acquaintance with facts, which makes a pedant, but in the use of facts, which makes a philosopher."

But though facts are only the 'body of science,' while 'the ideas' and the conclusions they suggest are its soul, they are thus shown to be of primary and indispensable importance in the construction of a science —like the bricks or blocks of stone of which an ediTRUE VALUE OF FACTS IN SCIENCE. 15

fice is constructed. But those who are satisfied with merely discovering and contributing facts, and leaving them for others to use, are the mere hewers of stone and the brick-makers, in science; while the master masons are those who assign to each fact its place and its value, and thus really build up the structure required. Some of the most distinguished philosophers and discoverers did nothing themselves towards obtaining the facts on which their discoveries were based. Newton, in a letter to Flamstead, remarked: "All the world knows I make no observations myself; and if I do not make a handsome acknowledgment, they will reckon me an ungrateful clown." Harvey did not himself discover a single one of the facts on which his discovery of the circulation of the blood reposed. To discover facts requires a high development and much practice of the perceptive faculties—of the senses ; to deduce conclusions requires superior and well exercised reasoning powers; and these two diverse qualifications are but rarely blended in the same mind. Each is, however, of great value in its place, and both are indispensable to the advancement of science; though the latter performs the higher and the crowning function.

COMPARATIVE CHARACTER AND QUALITY OF MEDICAL

SCIENCE.

III. In respect to the comparative character and quality of the science to which we are devoted, it has already been remarked that as a whole it is a science of probability, and, with the exception made,

cannot from its very nature become an exact or positive science. It is often repeated that medicine is an inductive science, and therefore to be classed with Astronomy, Physics, and Chemistry, and other mere physical sciences. But of the several distinct departments of medical science not one is exclusively inductive, and no two are equally so.

Since, however, they are all in some degree inductive, none of them but descriptive anatomy made any considerable progress till the inductive method of acquiring knowledge was distinctly recognized and began to be appreciated. It therefore becomes necessary to inquire what is meant by the inductive method, and when and by whom its application to the advancement of the sciences termed the inductive, was suggested.

THE METHODS OF SCIENCE—INDUCTION AND DEDUCTION.

I. An inductive science is one, it is said, which is advanced, or in which truth is obtained, by induction. What, then, is induction? or, to use a synonymous expression, what is the inductive process? Some would reply that induction is a peculiar process of reasoning; but this is not the fact. The peculiarity affects only the manner in which we obtain the data from which we reason, as will presently appear.

There are but two scientific methods of obtaining truth:—1st. To proceed from the external to the internal, from facts to conclusions, from effects to causes; 2d. The reverse of this—to proceed from INDUCTION AND DEDUCTION. 17

the internal to the external, from principles to facts, from causes to effects. The first is the inductive process, and is an a posteriori mode of reasoning; the second, the deductive or rational, or reasoning a priori. The inductive reasoner "rises from facts to the principle or law which governs them;" the deductive "draws the principle or law from ideas (not facts) already in his mind, and explains the facts hy descending on them, instead of rising from them." The latter, therefore, necessitates a theory, or at least a general proposition, to start with; the former excludes theory entirely. The inductive method gives the first place to facts; the deductive, or rational, to ideas, or general propositions. Both alike include a reasoning process, neither of them being mere investigation ;* and both are alike indispensable to the completion of every science, since each has its own peculiar mission to fulfill; and they sometimes follow each other as successive steps in the attainment of a particular scientific result. The reasoning process is the same in both; the "induction" consisting merely in the collecting and bringing into the account, one by one, the facts on which we reason. The inductive process, then, consists of—1st, the induction, as just explained; and 2d, the deduction—i. e., drawing the conclusion from the facts. We therefore reason from, but not by, induction. We can never attain to certainty, but only to probability, by either of these methods. Hence, the con

diseases as there are individuals—deduce the general conclusion that this class of people is liable to colic, typhus fever, or pleurisy. Evidently, if we are to deduce any general conclusion in regard to a particular disease, the instances compared must all be instances of the disease in question. On the other hand, if we are to draw any general conclusion as to the effect of a particular calling or avocation, the instances adduced must all be examples of the same avocation.

Still, no one but an adept in the particular department of science can judge accurately of the precise nature and comparability of the facts pertaining to it. A physiologist alone can rightly collate physiological facts, preparatory to making a logical deduction therefrom; and the chemist has the same exclusive judgment in regard to chemical facts. And neither can assume the place of the other without some risk to the science on which he trespasses, unless he at the same time thoroughly understands the latter also.

3. But the probability of a conclusion obtained by the inductive method also depends much upon the number of similar facts adduced. In general, we may say the number must be sufficient to warrant the conclusion. "We must have enough instances to serve as a sample. But different minds will require different numbers to satisfy them as a basis for deduction; and different departments of science are very diverse in this respect. In physics or natural philosophy, a single instance will sometimes (though rarely) warrant a conclusion; in physiology and