which reflects the images of things exactly as they are; it is like a mirror of an uneven surface, which combines its own figure with the figures of the objects it represents.'

Among the idols of this class we may reckon the propensity which there is in all men to find a greater degree of order, simplicity, and regularity, than is actually indicated by observation. Thus as soon as men perceived the orbits of the planets to return into themselves, they immediately supposed them to be perfect circles, and the motion in those circles to be uniform; and to these hypotheses the astronomers and mathematicians of all antiquity laboured incessantly to reconcile their observations.

The propensity which Bacon has here characterized may be called the spirit of system.

2. The Idols of the Den are those which spring from the peculiar character of the individual. Besides the causes of error common to all mankind, each individual has his own dark cavern, or den, into which the light is imperfectly admitted, and in the obscurity of which a tutelary idol lurks, at whose shrine the truth is often sacrificed.

Some minds are best adapted to mark the differences of things, others to catch at the resemblances of things. Steady and profound understandings are disposed to attend carefully, to proceed slowly, and to examine the most minute differences; while those that are sublime and active are ready to lay hold of the slightest resemblances. Each of these easily runs into excess; the one by catching continually at distinctions, the other at affinities.

3. The Idols of the Forum are those which arise

out of the intercourse of society, and those also which arise from language.

Men believe that their thoughts govern their words; but it also happens by a certain kind of reaction that their words frequently govern their thoughts. This is the more pernicious that words being generally the work of the multitude divide things according to the lines most conspicuous to vulgar apprehensions. Hence when words are examined, few instances are found in which, if at all abstract, they convey ideas tolerably precise and defined.

4. The Idols of the Theatre are the deceptions which have arisen from the dogmas of different schools.

As many systems as existed, so many representations of imaginary worlds had been brought upon the stage. Hence the name of Idola Theatri. They do not enter the mind imperceptibly like the other three; a man must labour to acquire them, and they are often the result of great learning and study.

After these preliminary discussions Bacon proceeds in the Second Book of his Organum to describe and exemplify the nature of induction.

The first object must be to prepare a history of the phenomena to be explained, in all their modifications and varieties. This history is to comprehend not only all such facts as spontaneously offer themselves, but all the experiments instituted for the sake of discovery or for any of the purposes of the useful arts. It ought to be composed with great care; the facts accurately related and distinctly arranged; their authenticity diligently examined; those that rest on doubtful evidence though not

rejected, yet noted as uncertain, with the grounds of the judgment so formed. This last is very necessary, for facts often appear incredible only because we are ill-informed, and cease to appear marvellous when our knowledge is further extended. This record of facts is Natural History.

The Natural History being prepared of any class of phenomena, the next object is to discover, by a comparison of the different facts, the cause of these phenomena, or, as Bacon calls it, the form. The form of any quality in a body is something convertible with that quality; that is, where it exists the quality exists: thus if transparency in bodies be the thing inquired after, the form of it is something found wherever there is transparency. Thus form differs from cause in this only: we call it form or essence when the effect is a permanent quality; we call it cause when the effect is a change or an event.

Two other objects, subordinate to forms, but often essential to the knowledge of them, are also occasionally subjects of investigation. These are the latent process, latens processus; and the latent schematism, latens schematismus. The former is the secret and invisible progress by which sensible changes are brought about, and seems in Bacon's acceptation to involve the principle since called the law of continuity, according to which no change however small can be effected but in time. To know the relation between the time and the change effected in it would be to have a perfect knowledge of the latent process. In the firing of a cannon, for example, the succession of events during the short interval between the application of the match and the expulsion of the ball, consti

tutes a latent process of a very remarkable and complicated nature, which, however, we can now trace with some degree of accuracy.

The latent schematism is that invisible structure of bodies on which so many of their properties depend. When we inquire into the constitution of crystals, or into the internal structure of plants, &c., we are examining into the latent schematism.

In order to inquire into the form of anything by induction, having brought together all the facts, we are to begin with considering what things are thereby excluded from the number of possible forms. This conclusion is the first part of the process of induction. Thus if we are inquiring into the quality which is the cause of transparency in bodies; from the fact that the diamond is transparent, we immediately exclude rarity or porosity as well as fluidity from these causes, the diamond being a very solid and dense body.

Negative instances, or those where the form is wanting to be also collected.

That glass when pounded is not transparent is a negative fact when the form of transparency is inquired into; also that collections of vapours have not transparency. The facts thus collected, both negative and affirmative, should, for the sake of reference, be reduced to tables.

Bacon exemplifies his method on the subject of Heat; and though his collection of facts be imperfect, his method of treating them is extremely judicious,* and the whole disquisition highly interesting.

* A different opinion from that of Prof. Playfair respecting this investigation will be hereafter quoted from John

Mill.

After a great many exclusions have been made, and left but few principles common to every case, one of these is to be assumed as the cause; and by reasoning from it synthetically we are to try if it will account for the phenomena. So necessary did this exclusive process appear to Bacon that he says, "It may perhaps be competent to angels or superior intelligences to determine the form or essence directly, by affirmations from the first consideration of the subject; but it is certainly beyond the power of man, to whom it is only given to proceed at first by negatives, and in the last place to end in affirmatives, after the exclusion of everything else."

There is, however, great difference in the value of facts. Some of them show the thing sought for in the highest degree, some in the lowest; some exhibit it simple and uncombined, in others it appears confused with a variety of circumstances. Some facts are easily interpreted, others are very obscure, and are understood only in consequence of the light thrown on them by the former. led Bacon to his consideration of Prerogative Instances, or the comparative value of facts as means of discovery. He enumerates twenty-seven different species; but we must content ourselves with giving only the most important.

This

I. Instantia solitaria: which are either examples of the same quality existing in two bodies otherwise different, or of a quality differing in two bodies otherwise the same. In the first instance the bodies differ in all things but one; in the second they agree in all but one. Thus if the cause or form of colour be inquired into, instantiæ solitaria are found in crystals, prisms, drops of