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to range itself under the terms of a supposed law, that fact demonstrates the invalidity of any hypothesis.
Particular stress is laid upon this point for the reason that, as before remarked, it seems to have been lost sight of in many quarters where one would expect to find the strictest rules of scientific investigation rigidly enforced. Newton fully appreciated the weight and importance of the distinction, as is shown by the fact that he long delayed the publication of the "Principia," because of the apparent refusal of one phenomenon to submit to the terms of his hypothesis; and not until it was demonstrated by subsequent discovery that the apparent exception did not exist, did he venture to give to the world the theorem which made his name immortal.
Having established a general principle or law by induction, the process of deduction begins; and if no fact remains to negative the principle, we can take our stand upon the constancy of Nature and the immutability of her laws, and confidently explain the past and predict the future. And this is the test of the correctness of an hypothesis, that it enables one skilled in the science to which it appertains to predict correctly, to state with scientific certainty what will happen under a given state of circumstances. Thus a knowledge of the laws pertaining to the movement of the heavenly bodies enables the astronomer to predict the phases of the moon and the eclipses with mathematical exactitude. We may take the science of astronomy as an illustration of the processes of inductive reasoning and of all scientific investigation. By the accurate observation of facts for a long series of years by many and independent observers; by comparison of the results of their observations, and by a system of checking, tabulating, verification, and revision constantly employed, aided by the genius of such men as Kepler and Newton, the Copernican system of astronomy was finally wrought out, and the laws govern
ing planetary motion were formulated. This was induction, - reasoning from particular facts up to general principles or axioms. By deduction, the astronomer, taking as his premises these general principles thus established (the constancy of Nature being always assumed), is enabled to explain all the salient features of planetary motion, and to predict with unerring accuracy the phenomena of the future. On the other hand, the Ptolemaic system, which preceded the Copernican, may serve as an illustration of the defective methods of the ancients, arising from inaccurate observation, insufficient verification, and premature generalization.
It must not be understood that, because Bacon was the first to discover and formulate the law of inductive reasoning, he was the first to reason inductively. Men had always reasoned by that method, more or less. Nor must it be inferred that, because he was the first to discover and make known the true value of a fact as an element of logic, he was the first to employ facts as a basis of reasoning. The first man who ever observed the sun rising at one point of the compass and setting at the opposite, observed three hundred and sixty-five facts every year, from which he reasoned inductively up to the general principle, that the sun rises in the east and sets in the west; and he was enabled to predict, from day to day, that the sun would continue so to rise and set. It so happened that the man was approximately right, having observed a sufficient number of facts to justify his belief. But the same man, doubtless, was equally certain that the earth was flat, and that his horizon marked the boundaries of the habitable world. In this he was wrong, and his error arose from defective observation of an insufficient number of facts. Nor in this was he alone. His defective methods of reasoning, differing only in degree and not in kind, were shared by all his contemporaries, and by all his successors, great and small, down to the days of Plato and Aristotle, and
from Plato and Aristotle down to the days of Queen Elizabeth.
Until that time all men reasoned by defective methods; for the fundamental law of reasoning had not been discovered. Hence the wisdom of a Socrates or a Plato afforded no protection against the fatal error of deducing the most momentous conclusions from assumed premises; nor could the logic of Aristotle, which, as Bacon declares, "corrupted natural philosophy," prevent him from "constructing the universe out of his Categories." The wisdom of the Greeks, according to Bacon, was disputatious; their science was spectacular; their history was composed largely of tales and rumors of antiquity, and they were always more intent on founding sects and systems of philosophy, and fighting for supremacy in wrangling, than zealous in their search for truth. Their teachings, therefore, often seemed to justify the charge of Dionysius against those of Plato, that they were "the words of idle old men to inexperienced youth;" and of the Egyptian priest who said of the Greeks that "they were ever children, and had neither antiquity of knowledge nor knowledge of antiquity;" and of Bacon, who, quoting the above, added, "And surely in this they are like children, they are ready to chatter, but cannot beget."
Nevertheless, no one can fail to appreciate the subtlety of their philosophy, the vigor of their intellects, or the virility of their manhood, whatever may be said of the soundness of their methods of searching for truth. In spite of defective processes of reasoning they have bequeathed to posterity an immortal literature, a deathless fame, and a philosophy which, in many instances, demonstrates an intuitive perception of truths which modern science can only illustrate and confirm. But of true science they had nothing worthy of the name. Like their philosophy, it was
1 Novum Organum.
speculative, and hence was unable to withstand those everpresent reactionary forces which impel the human mind to rebel against any system of science, philosophy, or belief not based upon observable phenomena or demonstrable propositions.
Hence it was that all the learning and the philosophy, all the arts and the civilization of ancient Greece and Rome could not avert their decadence, nor rescue the intellectual world from the dismal horrors of the long night of mediæval barbarism. It is a common remark that the physical effeminacy of the people of ancient Rome, resulting from the luxurious habits engendered by the refinements of their civilization, rendered them an easy prey to the hordes of vigorous barbarians of Northern Europe, and was thus the primary cause of their downfall. Other instances exist where ancient civilizations have risen and flourished and fallen. Every year fresh discoveries are made of the remains of prehistoric civilizations which must have been in decay, if not extinct, long before tradition began. And in every case, historic or prehistoric, there exist evidences that their extinction was the result of practically the same causes as those which led to the downfall of the Roman Empire. From these facts it has been argued that there must exist a natural law pertaining to civilization analogous to the law of organic nature; namely, that growth results in maturity, maturity in degeneracy, and degeneracy in disintegration,— in other words, that the law of human development is not the law of constant progress, but that civilization moves in successive cycles. Such reasoners look with gloomy foreboding upon the present state of progress in science and the arts as a sure precursor of the imminent decadence of those nations who have attained the higher civilization, and of their ultimate relapse into barbarism.
I cannot so interpret the history of mankind. Our present civilization is built upon a radically different foundation
from that of any of the nations whose history may be cited as a precedent. The difference may be illustrated by a single reference. Taking Greece as an example presenting the most striking contrast between the highest degree of her enlightenment and the lowest degree of her degeneracy, the most obvious fact pertaining to the character of her civilization is this: that in not one of the arts or sciences in which she excelled the most barbarous nations which surrounded her was there a single element of power that could give promise of national perpetuity, or even of substantial national progress. The Greeks excelled in philosophy, but it was almost purely speculative, and was therefore subject to the law of reaction. Their science was as speculative as their philosophy, and subject to the same law. They excelled in mathematics, but in the absence of other sciences, of which mathematics is but the handmaiden, it was not an element of power. They excelled in art and in literature, but in neither was there an element of national strength; for though the art of Phidias has never been surpassed, and Homer's rank after the lapse of ages is unchallenged, the sculptor's chisel and the poet's tablet were poor weapons of defence against the superior physical force of their enemies.
On the other hand, the civilization of the present day is founded upon the inductive sciences. In the inductive sciences the law is that of eternal progress. In them there is no possible element of reaction. A proposition or principle of natural philosophy, once established, is as firmly fixed as a proposition in mathematics, and is never afterwards disputed. Every step, therefore, is a step in advance. Every new demonstration of a law of Nature furnishes the basis for a fresh start in a thousand different directions. There is, therefore, no possibility that, either in the purely demonstrative or in the purely experimental sciences, the world can ever again go backward, and there is as little probability that it will ever stand still.