The propensity which Bacon has here characterized so,well, is the same that has been, since his time, known by the name of the spirit of system. The prediction, that the sources of error would return, and were likely to infest science in its most flourishing con dition, has been fully verified with respect to this illusion, and in the case of sciences which bad no existence at the time when Bacon wrote. When it was ascertained, by ob servation, that a considerable part of the earth's surface consists of minerals, disposed in horizontal strata, it was immediately concluded, that the whole exterior crust of the earth is composed, or has been composed, of such strata, continued all round without interrup tion ; and on this, as on a certain and general fact, entire theories of the earth have been constructed.
There is no greater enemy which science has to struggle with than this propensity of the mind ; and it is a struggle from which science is never likely to be entirely relieved ; because, unfortunately, the illusion is founded on the same principle from which our love of knowledge takes its rise.
2. The idols of the den are those that spring from the peculiar character of the indi vidual. Besides the causes of error which are common to all mankind, each individual, according to Bacon, 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.
One great and radical distinction in the capacities of men is derived from this, that some minds are best adapted to mark the differences, others to catch the resemblances, of things. Steady and profound understandings are disposed to attend carefully, to pro ceed 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.
The studies, also, to which a man is addicted, have a great effect in influencing his opinions. Bacon complains, that the chemists of his time, from a few cxperiments ovith the furnace and the crucible, thought that they were furnished with principles sufficient to explain the strficture of the universe ; and he censures Aristotle for having depraved his physics so much with his dialectics, as to render the fdrmer entirely a science of words and controversy. In like manner, he blames a philosopher of his own age, Qilbert, who had studied magnetism to godd purpose, for having proceeded to form out of it a general system of philosophy. Such things have occurred in every period of science. Thus elec
tricity has been applied to explain the motion of the heavenly bodies ; and, of late, gal vinism and electricity together have been held out as explaining, not only the affinities of chemistry, but the phenomena of gravitation, and the laws of vegetable and animal life. It were a good caution for a man who studies nature, to distrust those things with which he is particularly conversant, and which he is accustomed to contemplate with pleasure.
3. The idols of theArum are those that arise out of the commerce or intercourse of so: ciety, and especially from language, or the means by which men communicate their thoughts to one another.
Men believe that their thoughts govern their words ; but it also happens, by a certain kirid 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 well.defined. For such imperfections there seems to be no remedy, but by having recourse to particular. instances, and diligently comparing the meanings of words with the external archetypes from which they are derived.
4. The idols of the,theatre are the last, and are the deceptions which have taken theirriee from the systems or dogmas of the different schools of .philosophy. In the opinion of Bacon, as many of these systems as had been invented, so many representations of iw&. ginary 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.
" Philosophy," said he, " as hitherto pursued, has taken much from a few things, or a little from a great many ; and, in both cases, has too narrow a basis to be of much dura 6 tion or utility." The Aristotelian philosophy is of the latter kind ; it has taken its prin ciples from common experience, but without due attention to the evidence or the precise nature of the facts ; the philosopher is left to work out the rest from his own invention. Of this kind, called by Bacon the sophistical, were almost all the physical systems of an tiquity.