by enlarged benevolence, it designates a man who was created for the benefit of his race.

It is important to observe the relation which a philosophical imagination sustains to the reasoning power in our investigation of truth.

I have said that reasoning is the process by which we pass from the known to the unknown, and thus transform the unknown into the known. Suppose the philosopher to stand on the utmost limits of the known. His reason is prepared either to prove or disprove any proposition that may be presented. But there is no proposition presented. There is nothing within the cognizance of the understanding, but on the one side the known, and, on the other, absolute silence and darkness. Reason presents no proposition. Its sole province is either to prove or disprove what is placed before it. None of the other faculties which we have considered can present propositions to the reason, as the matter on which its powers shall be exerted. Hence the necessity of the imagination. Its office is to pass beyond the limits of the known, and form a conception which may be true of something in the unknown. This it presents in the shape of a proposition or a philosophical conception. As soon as this is done, an opportunity is offered for the exercise of the reasoning faculty. There is something now to be proved, and there may be something by which to prove it. We at once endeavor to discover some media of proof which may show a necessary connection between what is known, and this proposition which is, as yet, unknown. Until this connection can be shown, our proposition is a mere suggestion, a theory, an hypothesis. As soon as this connection has been established, what was before hypothesis becomes acknowledged truth, and by just so much is the dominion of science extended.

Or, to express the same idea in another form, experiment,

or the attempt to discover new truth, is nothing more than

putting questions to nature.
definite object of inquiry.
answer at all, is always either yes or no. Philosophical
imagination enables us to put the question in a form capable
of a definite answer. It suggests a conception which may
be true or false, but which must be either one or the other.
By experiment or demonstration we put the question to
nature, and receive her answer either affirmative or nega-
tive. If the answer be negative, we surrender our proposi-
tion as worthless, and the imagination suggests another, and
another, until an affirmative answer is received. The work
is then accomplished, and a new truth is added to the sum
of human knowledge.

But a question supposes some
The answer of nature, if she

Thus the conceptions of Ptolemy and of Copernicus were both mere hypotheses of equal value, until one was proved to be true. The conception of Newton, that the motions of the bodies which compose the solar system are all subjected to the law of gravitation, was a mere hypothesis, a creation of the imagination, until it was scientifically established. He himself so considered it, and I believe never mentioned it until he had proved it. He considered it merely a question which he had put to nature, unworthy of attention until he had received an affirmative answer. At first, he supposed that the answer which he received was negative. Taking for one element of his calculations the length of a degree of the earth, as it had been measured by the French mathematicians, he found that his hypothesis could not be established, and he laid it aside for several years. A new and more accurate measurement was afterwards obtained, which brought to his recollection his almost forgotten computations. He commenced them anew, with more accurate data, and soon arrived at the result which added his name to the brief list of those who must always be remembered.

The same process must be performed in every case where a scientific truth is discovered. The proposition of the squares on the sides of a right-angled triangle was a mere hypothesis to Pythagoras until he had demonstrated its truth.

The

These illustrations have referred to science. The truth here suggested is, however, of wider application. Thus, the ingenious inventor has become acquainted with some natural law which he believes may be rendered available for the service of man. He must form in his own mind a concep tion of the manner in which this result may be accomplished. At first a rough draft is present before him. He perceives its imperfections, and labors to correct them. One and another plan suggests itself, until he has before him a whole system of arrangements by which the result may be attained. Months of anxious thought were consumed by Watt and Fulton before they perfected those conceptions, which, when realized in the form of inventions, have revolutionized the manufactures and commerce of the world. same remark will apply to a military commander, who, before a sword is drawn, must form in his mind the whole plan of a campaign. Thus it is that an act of the imagination must precede every other, when an important truth is to be discovered, or great enterprise to be achieved. We must, first of all, form a conception of what we would do, or prove, and of the means by which it is to be accomplished. We may, it is true, fall short of our ideal; but, except by accident, we cannot go beyond it. Hence this creative power lies at the foundation of all great excellence. Other things being equal, he will certainly arrive at the most eminent success, who is able to take the largest, most comprehensive, and most truthful views of that which he desires to accomplish.

I shall close this chapter by a few suggestions on the mode of improving a philosophical imagination.

It is obvious that this power, to be of any practical value must derive its materials from essential truth. Fancies car. never form the elements of a philosophical imagination. We desire to discover truth; but truth can only be discovered by means of truth. The more thoroughly, therefore, we are acquainted with the known, the more easily shall we discover the regions which may be reclaimed from the unknown. He will be more likely to extend the limits of human knowledge who has made himself acquainted with already discovered truth. Newton, at an early age, was familiar with all that was then known of the science of astronomy; and this knowledge pointed out to him the line in which discovery was to be made. Columbus was profoundly learned in the geography of his age. He was intimately acquainted with all that had been discovered of the figure of the earth, and the proportions in which its surface was covered with land and water. This knowledge first suggested to him the idea of a new continent. Had he known of nothing beyond the shores of the gulf of Genoa, his mind could never have formed this magnificent conception, and after-ages would never have heard of the "world-seeking Genoese."

2. I have before remarked the power of generalization to aid in the discovery of truth. We may here observe the mode in which it tends to this result. Every object in nature, every change, every law, is the type of a class more numerous than we are able to conceive. These types are repeated and diversified in infinite variety, but they are all characterized by the same essential elements, unseen, it may be, by the casual observer, but understood by the far-sighted interpreter of nature. He who is able to distinguish the essential elements of a type from its accidental circumstances, trace them out through their various manifestations, and expand them to their widest generalizations, will find his mind replete with conceptions of all possible truth. Gen

eralization pointed out to Newton those conceptions which led to most of his discoveries, and also gave rise to many suggestions which were not proved to be discoveries until more than a century after his death. In his experiments on light, he observed that the refracting power of different bodies was in proportion to their combustibility, and that the diamond possessed the former power in an unusual degree. Applying this law to this particular case, he was led to conceive that the diamond itself might be combustible. Though a mineral, and the hardest of known substances, he disregarded these accidents, and, boldly generalizing his idea, predicted a discovery which only a few years since has been established.

3. In the works of a great artist, there is always to be observed a manner peculiar to himself, which a true connoisseur will readily detect. We call this peculiarity the style of an author or an artist. It is derived from the intellectual and moral character of the individual, and is that which renders his outward works the index of his inward and spiritual mind. It is natural to suppose that this peculiarity should be apparent in the works of the Creator. There is a speciality in his mode of treating subjects, a style which designates all the works of his hand. He who, by deep and profound reflection on the works of God, has become most familiar with the laws of that which we call nature, and with the relations which these laws sustain to each other, will be the most likely to penetrate into the unknown, and originate those conceptions which lead to the discovery of truth. The further he advances in his investigations, the richer will be the field of discovery that opens before him.

If I may be allowed, I will use an illustration which I once employed when treating on this subject. "Suppose I should present before you one of the paintings of Raphael, and, covering a part of it with a screen, ask you to proceed