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travelled through distant countries, who has collected a vast number of plants, who knows their names, their peculiarities, and their medicinal qualities, is not yet a botanist, but only a herbalist, a lover of plants, or what the Italians call a dilettante, from dilettare, to delight. The real science of plants, like every other science, begins with the work of classification. An empirical acquaintance with facts rises to a scientific knowledge of facts as soon as the mind discovers beneath the multiplicity of single productions the unity of an organic system. This discovery is made by means of comparison and classification. We cease to study each flower for its own sake; and by continually enlarging the sphere of our observation, we try to discover what is common to many and offers those essential points on which groups or natural classes may be established. These classes again, in their more general features, are mutually compared ; new points of difference, or of similarity of a more general and higher character, spring to view, and enable us to discover classes of classes, or families. And when the whole kingdom of plants has thus been surveyed, and a simple tissue of names been thrown over the garden of nature ; when we can lift it up, as it were, and view it in our mind as a whole, as a system well defined and complete, we then speak of the science of plants, or botany. We have entered into altogether a new sphere of knowledge where the individual is subject to the general, fact to law ; we discover thought, order, and purpose pervading the whole realm of nature, and we perceive the dark chaos of matter lighted up by the reflection of a divine mind. Such views may be right or wrong. Too hasty comparisons, or too narrow distinctions, may have prevented the eye of the observer from discovering the broad outlines of nature's plan. Yet every system, however insufficient it may prove hereafter, is a step in advance. If the mind of man is once impressed with the conviction that there must be order and law everywhere, it never rests again until all that seems irregular has been eliminated, until the full beauty and harmony of nature has been perceived, and the eye of man has caught the eye of God beaming out from the midst of all His works. The failures of the past prepare the triumphs of the future.

Thus, to recur to our former illustration, the systematic arrangement of plants which bears the name of Linnæus, and which is founded on the number and character of the reproductive organs, failed to bring out the natural order which pervades all that grows and blossoms. Broad lines of demarcation which unite or divide large tribes and families of plants were invisible from his point of view. But in spite of this, his work was not in vain. The fact that plants in every part of the world belonged to one great system was established once for all; and even in later systems most of his classes and divisions have been preserved, because the conformation of the reproductive organs of plants happened to run parallel with other more characteristic marks of true affinity. It is the same in the history of astronomy. Although the Ptolemæan system was a wrong one, yet even from its ec

1 " The generative organs being those which are most remotely related to the habits and food of an animal, I have always regarded as affording very clear indications of its true affinities.” – Owen, as quoted by Darwin, Origin of Species, p. 414.

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centric point of view, laws were discovered determining the true movements of the heavenly bodies. The conviction that there remains something unexplained is sure to lead to the discovery of our error.

There can be no error in nature; the error must be with us. This conviction lived in the heart of Aristotle when, in spite of his imperfect knowledge of nature, he declared that there is in nature nothing interpolated or without connection, as in a bad tragedy;” and from his time forward every new fact and every new system have confirmed his faith.

The object of classification is clear. We understand things if we can comprehend them; that is to say, if we can grasp and hold together single facts, connect isolated impressions, distinguish between what is essential and what is merely accidental, and thus predicate the general of the individual, and class the individual under the general. This is the secret of all scientific knowledge. Many sciences, while passing through this second or classificatory stage, assume the title of comparative. When the anatomist has finished the dissection of numerous bodies, when he has given names to each organ, and discovered the distinctive functions of each, he is led to perceive similarity where at first he saw dissimilarity only. He discovers in the lower animals rudimentary indications of the more perfect organization of the higher; and he becomes impressed with the conviction that there is in the animal kingdom the same order and purpose which pervades the endless variety of plants or any other realm of nature. He learns, if he did not know it before, that things were not created at random or in a lump, but that there is a scale which leads, by imperceptible degrees, from the lowest infusoria to the crowning work of nature, man ; that all is the manifestation of one and the same unbroken chain of creative thought, the work of one and the same all-wise Creator.

In this way the second or classificatory leads us naturally to the third or final stage — the theoretical, or metaphysical. If the work of classification is properly carried out, it teaches us that nothing exists in nature by accident; that each individual belongs to a species, each species to a genus ; and that there are laws which underlie the apparent freedom and variety of all created things. These laws indicate to us the presence of a purpose in the mind of the Creator ; and whereas the material world was looked upon by ancient philosophers as a mere illusion, as an agglomerate of atoms, or as the work of an evil principle, we now read and interpret its pages as the revelation of a divine power, and wisdom, and love. This has given to the study of nature a new character. After the observer has collected his facts, and after the classifier has placed them in order, the student asks what is the origin and what is the meaning of all this ? and he tries to soar, by means of induction, or sometimes even of divination, into regions not accessible to the mere collector. In this attempt the mind of man no doubt has frequently met with the fate of Phaeton ; but, undismayed by failure, he asks again and again for his father's steeds. It has been said that this so-called philosophy of nature has never achieved anything ; that it has done nothing but prove that things must be exactly as they had been found to be by the observer and collector. Physical science, however, would never have been what it is without the impulses which it received from the philosopher, nay even from the poet. “At the limits of exact knowledge ” (I quote the words of Humboldt), “as from a lofty island-shore, the eye loves to glance towards distant regions. The images which it sees may be illusive ; but, like the illusive images which people imagined they had seen from the Canaries or the Azores, long before the time of Columbus, they may lead to the discovery of a new world.”

Copernicus, in the dedication of his work to Pope Paul III. (it was commenced in 1517, finished 1530, published 1543), confesses that he was brought to the discovery of the sun's central position, and of the diurnal motion of the earth, not by observation or analysis, but by what he calls the feeling of a want of symmetry in the Ptolemaic system. But who had told him that there must be symmetry in all the movements of the celestial bodies, or that complication was not more sublime than simplicity? Symmetry and simplicity, before they were discovered by the observer, were postulated by the philosopher. The first idea of revolutionizing the heavens was suggested to Copernicus, as he tells us himself, by an ancient Greek philosopher, by Philolaus, the Pythagorean. No doubt with Philolaus the motion of the earth was only a guess, or, if you like, a happy intuition. Nevertheless, if we may trust the words of Copernicus, it is quite possible that without that guess we should never have heard of the Copernican system. Truth is not found by addition and multiplication only. When speaking of Kepler, whose method of reasoning has been considered as unsafe and fantastic by his contemporaries as well as by later astronomers, Sir David Brewster remarks very

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