But if that process be regarded as satisfactory, it is surely equally permissible for a man of science occasionally to look over into the philosophic region, and survey the territory on that side also, so far as his means permit. And if philosophers object to this procedure, it must be because they have found by experience that men of science who have once transcended or transgressed the boundary are apt to lose all sense of reasonable constraint, and to disport themselves as if they had at length escaped into a region free from scientific trammels—a region where confident assertions might be freely made, where speculative hypothesis might rank as theory, and where verification was both unnecessary and impossible. The most striking instance of a scientific man who on entering philosophic territory has exhibited signs of exhilaration and emancipation, is furnished by the case of Professor Haeckel of Jena. In an eloquent and popular work, entitled _das Welt-Räthsel_, the World Problem, or "The Riddle of the Universe," this eminent biologist has surveyed the whole range of existence, from the foundations of physics to the comparison of religions, from the facts of anatomy to the freedom of the will, from the vitality of cells to the attributes of God; treating these subjects with wide though by no means superhuman knowledge, and with considerable critical and literary ability. This work, through the medium of a really excellent translation by Mr M'Cabe, and under the auspices of the Rationalist Press Association, has obtained a wide circulation in this country, being purchasable for six-pence at any bookstall; where one often finds it accompanied by another still more popular and similarly-priced treatise by the same author, a digest or summary of the religious aspect of his scientific philosophy, under the title _The Confession of Faith of a Man of Science_. Professor Haeckel's credentials, as a learned biologist who introduced Darwinism into Germany, doubtless stand high; and it is a great tribute to his literary ability that a fairly abstruse work on so comprehensive a subject should have obtained a wide notoriety, and have been welcomed by masses of thinking readers, especially by many among the skilled artisans, in this country. From several points of view this diffusion of interest is most satisfactory, since the spread of thought on serious topics is greatly to be welcomed. Moreover, there is a vast mass of information in these writings which must be new to the bulk of the inhabitants of these islands. There is also a great deal of criticism which should arouse professors of dogmatic theology, and exponents of practical religion, to a keener sense of their opportunities and responsibility. A view of their position from outside, by an able and unsparing critic, cannot but be illuminating and helpful, however unpleasant.