Duke of Argyll
 My sincere respect for Professor Huxley forbids me from following him into the field of personal polemics, even if this Review were a fitting place for such exercitations. There are, however, some points of general interest in his last article on which I wish to say a few words.
The first of these concerns the use which Professor Huxley makes of the word 'science.' In common parlance this word is now very much confined to the physical sciences, some of which may be called specially experimental sciences, such as chemistry, and others exact sciences, such as astronomy. But Professor Huxley evidently uses it in that wider sense in which it includes metaphysics and philosophy. Under cover of this wide sweep of his net, he assumes to speak with the special authority of a scientific expert upon questions respecting which no such authority exists either in him or in anyone else. It seems to be on the strength of this assumption that he designates as pseudo-science any opinion, or teaching, or belief, different from his own.
I will illustrate what I mean by an example. One of the most elaborate of Professor Huxley's own works is his volume on The Elements of Comparative Anatomy, published some twenty-three years ago. Comparative anatomy is one of the branches of the larger science of Biology in which Professor Huxley is an expert; and, like all the other branches which grow out of the one great stem of 'Life,' as a subject of physical investigation, it runs up into ideas and conceptions which belong to, or border on, the region of metaphysics. In that volume Professor Huxley deals with the well-known question of comparative anatomy whether the vertebrate skull can, or cannot, be interpreted' as a developed vertebra. Through an elaborate argument, strictly conducted on the observation and analysis of physical facts, Professor Huxley comes to the conclusion that this 'interpretation' breaks down. 'The vertebral hypothesis of the skull,' he says, 'seems to me to be altogether abolished.' Yet, whilst rejecting this particular interpretation,' he accepts and enforces the general conception that there is a complete unity of organisation '  between all vertebrate skulls, from the skull of a man down to the skull of a pike. Furthermore, Professor Huxley explains that by this unity of organisation' he means that all vertebrate skulls 'are organised upon a common plan.' Repeating the same idea in another place, he says, osseous skulls are constructed upon a uniform plan."1
Now, if not absolutely in this conclusion, yet on all the physical facts leading up to it, Professor Huxley is an authority in the strictest sense of the word. He is an original investigator, and if any other man were to contest his facts, or even his interpretation of them, without independent observation, Professor Huxley would be entitled to pronounce his opinions to be pseudo-science.'
But Professor Huxley's scientific conclusion may become itself the basis of a farther investigation, and in this farther investigation he maybe no authority at all. We are all entitled to ask as a question, not of physical science, but of philosophy, 'What are the conclusions involved in the mental recognition of a 'plan as explaining an observed unity of organisation in all vertebrate skulls?
This is a questionof the very highest interestin which Professor Huxley as a biologist is not necessarily an expert. That laboratory in which the mind analyses its own operations is a laboratory accessible to us allin which we can all work, though not with the microscope or the knife. And if in this higher sphere of investigation other men are able to reach conclusions which Professor Huxley disputes, it is at least possible that it is his contention, and not that of his opponent, which best deserves the pseudo' prefix. In his article on the Preacher of St. Paul's he ridicules the word archetype'2 as applied to the community of organisation of the vertebrate skeleton. Yet this term was applied to it by an expert in biological science quite as eminent as himself; and it needs no expert to see that his own word plan' as the best word to express the facts, stands exactly on the same level with archetype' as what he calls a realistic figment.'
I have dwelt upon this point because men are very apt to be intimidated by authorities in science,' when in reality no sort of authority exists. Professor Huxley talks about intellectual sins' quite in the language and spirit of the Vatican.3 I know a good many scientific men of the very highest standing who totally dissent from Professor Huxley's metaphysics and philosophy; and are by no means inclined to accept his expositions, even of physical science, when those expositions travel beyond the particular branch in which he is an original observer.
For example, Professor Huxley disputes the relation between the three laws of Kepler and the Newtonian law of gravitation, which in one chapter of a book published now some twenty years ago I have represented to exist. As that chapter has stood the test of  criticism fairly well on the whole, I was curious to know whether Professor Huxley's attack is founded on distinctions of any value. For this purpose I have applied to two mathematicians of the highest authority, not only in Britain but in the world. One of these says, 'It is certainly true that the three famous laws of Kepler turned out to be the necessary result of the Newtonian law of gravitation.' Another of these authorities says, 'The laws of Kepler tell us how a planet moves, but are absolutely silent as to the why. To Newton we owe the why. But this was a step not only of an infinitely higher order than that of Kepler, it was in a totally different field. The one was descriptive, the other explanatory.' This is exactly the kind of difference which I indicated between the two; and it explains the sense in which one physical law may be said to be higher than another. Fortified by this authority, I feel quite safe in pronouncing Professor Huxley's verbal distinctions upon this point to be worth less. The relation between laws' such as those of Kepler and laws such as that of gravitation is a relation substantially such as I have represented it to be.
Professor Huxley propounds some of those old logical difficulties which attach to all our conceptions, and still more to all our language, upon the relations between mind and matter, as if nobody else had ever heard of them, or as if nobody but a comparative anatomist can even handle them. He refers me to Dr. Foster's excellent textbook of physiologyI can assure the Professor that I know it well, and have made some recent use of it4for the purpose of clearing up confusions of thought in which his own philosophy abounds.
In conclusion, let me express a hope that Professor Huxley will yet do an important service to science, by entering in some detail upon a subject to which I have only alluded in passing, but in terms which have excited his astonishment. He says, most truly, that as is the case with all new doctrines, so with evolution, the enthusiasm of advocates has sometimes tended to degenerate into fanaticism, and mere speculation has, at times, threatened to shoot beyond its legitimate bounds.' These words indicate vaguely and tenderly, but significantly, a fact which I stated, and will again state with emphasis. There has been not merely a tendency to degeneration into fanaticism, but a pronounced development of it, and a widespread infection from it in the language of science. But it will be enough if Professor Huxley will explain fully what he means by this tendency,' and if he will specify wherein it has been shown. This is a work which has yet to be done. The knowledge of a great expert would help Professor Huxley to do it sooner than it could be done by others. They can only work with the materials which are supplied by such as he. It is a work which has begun, and 'which his own warnings have encouraged. Since he has authority  to deal with intellectual sins, let him convict, and lay bare, and anathemise this one which he treats so gently. The tendency of new doctrines to degenerate into fanaticism is one of the laws to be traced in the long history of human follies, and all those who help to resist it are among the benefactors of their kind. I trust Professor Huxley may yet be with us for many years to come, and that he may expand and emphasise the hints and warnings he has given.
1 P. 290.
2 P. 204.
3 P. 191.
4 Unity of Nature, chap. iii.
C. Blinderman & D. Joyce