against a theory which only partially succeeds in tracing these out in detail. The absolute universality of law, and the incredibility of any real departure from it, are conceptions so strongly favored by the whole current of modern thought, that it is fast becoming a recognized scientific necessity to discard the notion of special creative epochs, and to substitute for it the principle of the unbroken continuity of life. "When we see these lowest of all known forms [the rhizopods] standing alone at the very beginning of time, and man, the highest and noblest form, appearing at the end, and an unmistakable gradation, always upward, through the long ages, and along all the four lines of plan, what open mind can help imbibing, if not the Darwinian doctrine, at least the spirit of the theory of development? " * The great need of the development hypothesis at present is to be organized, to be put into a more definite, symmetrical, and philosophical shape than it has yet received; and we welcome the work of Mr. Spencer as at least an attempt in the right direction. Fragmentary thinking, leaving out of sight the larger relations of facts, and embracing theories on different subjects which are seen to be mutually inconsistent when brought into juxtaposition, can be tolerated only in the infancy of science; the absolute necessity of harmony and comprehensiveness of thought, as the condition of the only possible interpretation of Nature which shall truly mirror her universal order, and reveal her secret of perfect unity in boundless variety, forces itself on the mind more and more powerfully in proportion to the increase of human knowledge. Permanent repose in the midst of antagonistic ideas and unreconciled facts is impossible; and in no way does Philosophy, as co-ordinating intelligence, more irresistibly prove her right of eminent domain over the mind of man than by compelling science itself to become philosophical in spirit and in form. Of this constraining influence the systems of Auguste Comte and Herbert Spencer, each aiming at the unification of all positive science as an organic whole, are conspicuous illustrations. It is no disparagement to either of these thinkers, entitled as they are to so much praise for the grandeur of their purpose and the patient industry of its execution, to say that neither of their

* J. P. Lesley, Origin and Destiny of Man, 1868, p. 80.

systems is more than a contribution to the great work in hand. So mighty a task, requiring not only philosophical genius, but also encyclopedical knowledge, transcends the ability of any single intellect; it is a labor imposed upon humanity itself, to be accomplished only by the united toils of many generations of great thinkers. The value of each successive systematization of knowledge must be measured by the largeness of its plan, the adequacy of its method, and the fidelity with which the method is applied in the execution of the plan. But the practical utility of a philosophy which shall reveal to science the law of its own development, and thus enable it to work intelligently rather than instinctively in the accomplishment of its ends, will be incalculable; and it is a sure mark of intellectual narrowness to treat with contempt the effort to create such a philosophy.

In taking the idea of universal evolution as its organizing principle, Mr. Spencer has sketched for his philosophy the largest plan possible in the present state of human knowledge; and here lies the cardinal merit of his attempt. But in the adoption of a false method, namely, the interpretation of universal evolution as a purely mechanical process, and in the failure to follow boldly the idea of universal evolution to its logical consequences, we find the cardinal demerits of his attempt. We cannot here enter on any general discussion of these points; but we shall discover in the work under consideration ample evidence of their truth. In the "Principles of Biology," we shall see the clashing of incompatible ideas, and the unaccountable evasion of logical corollaries from admitted principles. Mr. Spencer has thus stopped short of putting the development hypothesis into self-consistent or philosophical shape, and disappointed expectations warranted by his own "First Principles." The numerous special excellences of these two volumes, both in design and execution, must not detain us at present, though we cordially recognize them in passing; our critique does not concern itself with special details, but relates to the general scope of the work, and its success or failure as an attempt to organize the science of Biology as part of the Synthetic Philosophy. Waiving all examination into its purely scientific character, of which adepts in science are the only

competent critics, we restrict ourselves to a definite inquiry, namely, whether it has succeeded in setting forth the "general truths of Biology as illustrative of the laws of Evolution." The extent of its success in this respect is the measure of its philosophical value.

The great questions of biology, considered in its philosophical aspect, are three: What is the origin of life in the first instance? What is the origin of species or the different forms of life? What are the causes of organic evolution in general? To each of these three questions two answers are given. Life is said to originate in the first instance either by natural evolution or by supernatural interposition in the course of Nature. Species are said to originate either by gradual transitions from one form to another or by the periodical introduction of absolutely new and underived forms. These unlike answers to the first two questions spring from unlike hypotheses. If consistent with itself, the development hypothesis attributes the origin of life in the first instance, and the origin of species or the various forms of life, to a natural and gradual process, while the hypothesis of special creations attributes both to supernatural volitional acts. The former epitomizes the history of the individual and of the species alike in the one word evolution (with its correlate, dissolution); the latter admits evolution in the individual, but denies it in the species, without, however, substituting anything intelligible in its place. Each hypothesis, therefore, admitting evolution as a fact more or less universal, is confronted by a third question, namely, What are the causes of organic evolution? To this third question many answers are given, which fall, nevertheless, into two general classes. The one class finds the causes of organic evolution solely in the direct or indirect action of cosmical forces external to the organism; the other class, fully recognizing the action of these external forces, finds a concurrent cause in forces which manifest themselves in the organism alone, and are therefore irreducible to known cosmical forces. Hence among biologists two great tendencies exist, which find expression in what may be designated as the mechanist and the vitalist theories. It is the recognition of the speciality of vital phenomena, as not accounted for solely by mechanical or phys

ico-chemical causes, and not by any means the fanciful speculations respecting the unknown causes of these phenomena in which some vitalists indulge, that constitutes the essence of the vitalist theory; and it is the negation of this speciality which distinguishes the mechanist theory from it. The vitalist theory includes the mechanist theory, with the exception of this negation, affirming its affirmations, but denying its denials. If we now inquire what relation the mechanist and vitalist theories bear to the development and special-creation theories, we find a curious reversal of natural affinities. The vitalist and special-creation theories are sometimes found associated in the supposed interest of dogmatic theology; while the mechanist and development theories are sometimes found associated in the opposite interest. But, philosophically, the vitalist theory is most closely allied to the development theory, and the mechanist theory to the theory of special creations. Regarding the evolution of the universe as a gradual change from homogeneity to heterogeneity, produced by natural forces which are at bottom diverse manifestations of a single inscrutable force, the spirit of the development theory, at least as generalized by Mr. Spencer, would seem to require the recognition of mechanical, physical, chemical, biological, psychological, sociological, and moral phenomena, as an ascending series of dynamical facts, which are reducible to unity, not by denying the essential diversity of the facts themselves, and thus ignoring the law of the series, but rather by tracing those connections of the facts which constitute them a series. If the cosmos is evolved as a universal whole by an immanent force, and not by a force operating ab extra, then, unless the law of evolution changes, those organized beings which exist in the cosmos as partial wholes must also be evolved by immanent forces. To place the primary cause of organic evolution outside the organism is a conception precisely analogous to the conception of a creator outside the universe, a conception which Mr. Spencer, at least, repudiates. The spirit of the development theory manifestly allies it with the vitalist rather than with the mechanist theory. In like manner, the spirit of the specialcreation theory, which regards the universe as originated by a First Cause external to the universe, not immanent in it, and

which imagines each newly created species to have been in some way fashioned out of plastic materials and then vivified from without by foreign influences, would seem to be identical with the spirit of the mechanist theory, which regards the organism as only a living machine, created by the direct and indirect action of external forces alone. The special-creationist, it is true, attributes to the creative power both intelligence and will, and maintains the origination of life to be due to miraculous intervention in the course of Nature, an assumption which the biological mechanist declines to make. But, regarding the organism as either supernaturally created or naturally evolved by external power, both look at it as practically a manufactured machine, and the resemblance is greater than the difference. Hence, we repeat, the mechanist theory is less closely allied to the development theory than to the theory of special creations, while the vitalist theory, maintaining the natural evolution of life by the reciprocal play of external and internal forces whose manifestations cannot be classified together, alone appears to harmonize with the spirit of the development theory.

In determining the value of a biological system based on the idea of evolution, it becomes necessary to consider the answers it gives to the three great questions of philosophical biology, namely: What is the origin of life in the first instance? What is the origin of the various forms of life? What are the general causes of organic evolution? From the answers which Mr. Spencer has given to these three questions we derive our estimate of the philosophical character of his "Biology."

The great work of Mr. Darwin, on the "Origin of Species," which has done so much towards perfecting the development hypothesis, is chiefly confined to the discussion of the second of these three questions, the first being intentionally ignored, and the last being considered only with reference to the causes of variability in species. It exhibits, therefore, certain theoretical lacunæ, which must be filled before the development hypothesis can become a general philosophy of organic evolution. For carrying out the avowed purpose of the work, the principles so powerfully advocated and so beautifully illustrated by Mr. Darwin are perhaps sufficient; it being taken for