Page:Dictionary of National Biography volume 02.djvu/367

 Bacon carefully be noted; for, on a hasty reading of the 'Novum Organum,' it might easily be supposed that Bacon's object was confined to an instauration of what we now call the natural sciences. He here, however, explicitly tells us that his method is applicable, and intended to be applied, to the whole realm of knowledge.

From the prefatory remarks of Book i., Bacon passes in Book ii. to a more formal and systematic exposition of his method. In the 11th Aphorism the real business of the book begins, and this and the next two aphorisms contain the celebrated inductive tables which, together with the 'exclusion or rejection of natures' of which an example is given in Aph. 18, constitute Bacon's principal apparatus for arriving at a knowledge of the 'form,' a word which in modern scientific terminology may usually be best replaced by the word 'cause.'

His own method is simply contrasted with the inductio per enumerationem simplicem, or method of induction then in vogue. This method consisted in merely accumulating instances presenting the phenomenon in question, without following any rule of selection. Instead of this hasty and haphazard kind of induction, it is the peculiar merit of Bacon to have conceived, and to a certain extent to have elaborated, a regular and scientific method, proceeding by way of elimination, and thus carrying up an effect to its cause or following a cause into its effects by a chain of demonstrative reasoning. This method he calls the method of exclusions or rejections, and it is in this device that he conceives the peculiar value and originality of his logical system to consist.

The path to be followed by the method of exclusions is, Bacon confesses, a long and intricate one (Aph. 16), and hence he proposes, for the present at least, to employ, as auxiliary and preparatory to it, other aids for the understanding (Aphs. 19, 21).

Before, however, describing these other aids, he hazards an hypothesis (Aph. 20) on the form of heat, based on the materials collected in the tables. This 'giving reins to the understanding, or first vintage' (permissio intellectus or vindemiatio prima), must be regarded as a sort of parenthesis, inserted, by way of encouragement and relief, during the conduct of the more stringent method of exclusions with its various aids. It seems to afford an example of that very process of 'flying off from sense and particulars to the widest generalisations,' which Bacon himself condemns in the First Book (see Nov. Org. book i. aph. 19). The result, however, is remarkable in the history of science. Anticipating the theory of heat now generally accepted, he defines it as 'a motion, expansive, restrained, and striving amongst the smaller particles of bodies.' Even the modern theory as to the undulatory character of this motion seems to be anticipated in the following passage, which is quoted with approbation by Professor Tyndall: 'The third specific difference is this, that heat is a motion of expansion, not uniformly of the whole body together, but in its ultimate particles; and at the same time checked, repelled, and beaten back, so that the particles acquire a motion alternative, perpetually (quivering, striving and struggling, and irritated by repercussion, whence springs the fury of fire and heat.'

In the 21st Aphorism he proceeds to enumerate 'the remaining helps of the understanding, as they promote the interpretation of nature and a true and perfect induction.' The only 'help' which Bacon describes is the 'Prerogatives of Instances ' (Prerogatives Instantiarum). These are so called from the 'tribus prærogativa,' which, being selected by lot, voted first in the 'comitia tributa' of the Romans, and thus not only afforded an indication of the mode in which the other tribes were likely to vote, but also frequently exercised a considerable influence on their decision. They are, as Sir John Herschel says, 'characteristic phenomena, selected from the great miscellaneous mass of facts which occur in nature, and which, by their number, indistinctness, and complication, tend rather to confuse than to direct the mind in its search for causes and general heads of induction. Phenomena so selected on account of some peculiarly forcible way in which they strike the reason, and impress us with a kind of sense of causation or a particular aptitude for generalisation, Bacon considers, and justly, as holding a kind of prerogative dignity, and claiming our first and especial attention in physical inquiries.' Far the most famous of all these instances are the crucial instances (instantise criicis), a term which is, perhaps, more widely used than any other technical term of inductive logic. According to the metaphor there are two or more ways before us, and the observation or experiment in question acts as a 'guide-post' (crux) in determining us which to take. A celebrated historical example is that by which Pascal demonstrated the weight of the atmosphere. After the description of the Prerogative Instances the 'Novum Organum' comes to an abrupt termination.

What, we may now ask, are the principal merits of this magnificent fragment? Perhaps the main interest now attaching to the