morals as correct without austerity and exemplary without ostentation. These estimates are certainly diverse, but possibly they are equally near the truth. Priestley was much more of an experimentalist than a philosopher. In religion as well as in science he sought novelties. Facts, and facts only, could satisfy him. But his caprice was as noticeable as his positiveness, and his logical inconsistencies were gross. A queer instance of this is found in his adherence to the theory of l- phlo- giston"—the supposed principle of inflammability, or the matter of fire in composition with other bodies — the absurdity of which was shown by his own discovery of oxygen. In theology, as we have seen, while main- taining the immortality of the soul, he denied its im- materiality. He was never widely trusted as a religious leader; although, because of his ability and unimpeach- able morality, and his eminence in science, his pulpit services were eagerly sought. His fame rests princi- pally on his pneumatic inquiries. But lie was encyclo- pedic in the range of his writings, which extend to between seventy and eighty volumes. Among them are works on general and ecclesiastical history and bi- ography, on language, on oratory and criticism, on relig- ion and metaphysics. Although many of his opinions were fanciful and manifestly erroneous, there was hardly a subject touched by his pen that was not the brighter and shapelier because of his genius. It is not now, however, for the first time remarked that the minds best fitted for prosecuting the labors of experimental philosophy are by no means those from which we expect light to be cast into the more obscure region of meta- physical analysis. " Priestley's mind was objective to an extreme; he could fix his faith upon nothing which had not the evidence of sense in some way or other im- pressed upon it. Science, morals, politics, philosophy, religion, all came to him under the type of the sensa- tional. The most spiritual ideas were obliged to be cast into a material mould before they could commend themselves to his judgment or conscience. His intellect was rapid to an extraordinary degree; he saw the bear- ings of a question according to its principles at a glance, and embodied his thoughts in volumes, while many other men would hardly have sketched out their plan. All this, though admirable in the man of action, was not the temperament to form the solid metaphysician; nay, it was precisely opposed to that deep, reflective habit, that sinking into one's own inmost consciousness, from which alone speculative philosophy can obtain light and advancement." As a man of science, he has left his mark upon the intellectual history of the century; but besides being a man of science, he aimed at being a metaphysi- cian, a theologian, a politician, a classical scholar, and a historian. With an amazing intrepidity he plunged into tasks the effective performance of which would have demanded the labors of a lifetime. With the charge of thirty youths on his hands, he proposes to write an ecclesiastical history, and soon afterwards ob- serves that a fresh translation of the Old Test, would " not be a very formidable task" (Butt, Life, 1, 42). He carried on all manner of controversies upon their own ground with Horslev and Badeoek, with his friend Price, with Beattie and the Scotch philosophers, with Gibbon and the sceptics, and yet often labored for hours a day at his chemical experiments. So discursive a thinker could hardly do much thorough work, nor really work out or co-ordinate his own opinions. It would be in vain, therefore, to anticipate any great force or original- ity in Priestley's speculations. At best he was a quick reflector of the current opinions of his time and class, and able to run up hasty theories of sufficient apparent stability to afford a temporary refuge amid the storm of conflicting elements. With such tendencies of mind, therefore, and living in an age the whole bearing of which was away from the ideal to the sensational, it is not surprising that Priestley entered with energy into those principles of Hartley from which he hoped to reduce all mental science to a branch of physical investigation.
The metaphysical position he assumed may be fully seen in his Examination of Reid, Beattie, and Oswald: in fact, it is summed up in one extraordinary sentence, where lie affirms that " something has been done in the field of knowledge by Descartes, very much by Mr. Locke, but most of all by Hartley, who has thrown more useful light upon the theory of the mind than Newton did upon the theory of the natural world." Priestley rested the truth of materialism upon two de- ductions. The first was that thought and sensation are essentially the same thing— that the whole variety of our ideas, however abstract and refined they may be- come, are, nevertheless, but modifications of the sensa- tional faculty. This doctrine had been more fully main- tained in Prance by Condillac, and is a crude anticipa- tion of the positive view. The second deduction was that all sensation, and, consequently, all thought, arises from the affections of our material organization, and, therefore, consists entirely in the motion of the material particles of which the nerves and brain are composed. It is but justice, however, here to add that Priestley did not push his materialism so far as to evolve any conclu- sions contrary to the fundamental principles of man's natural religion, or to invalidate the evidence of a future state; for in the full conviction of these truths he both lived and died. And instead of distinctly inferring with* modern positivists that we can show nothing of the ul- timate nature either of mind or body, Priestley adopted the view that the soul is itself material. According to his quaint illustration, it resembles a razor. The power of thought inheres in it as the power of cutting in the razor. The razor dissolved in acids is annihilated ; and, the body destroyed by putrefaction, the power of think- ing ceases. But the particles remain in each case; and the soul, like the razor, may again be put together (Price and Priestley On Materialism, p. 82). The advantage of this doctrine, according to Priestley, was that it con- firmed bishop Law's theory of the seat of the soul. The soul being, in fact, a piece of mechanism, is taken to pieces at death, and though it may afterwards be put together again by divine power, there is no ground for the superstitions embodied in the doctrine of purgatory. Moreover, it strikingly confirms the Socinian doctrine by removing all pretext for a belief in the pre-existence of Christ. To sum up, then, the precise influence of Priestley upon the progress of sensationalism in a few words, we may say that he succeeded in cutting the last tie which had held Hartley to the poor remains of spir- itualism; that he reduced the whole phenomena of mind to organic processes— the mind itself to a material organization, and mental philosophy to a physical sci- ence. The whole existing order of things being an elaborate piece of mechanism, we infer the Almighty mechanist by the familiar watch argument (Disquisi- tions, i, 187). Indeed, the Deity himself becomes almost phenomenal, and Priestley has considerable trouble in saving him from materiality. He denies that a belief in his immateriality would increase our reverence for him (ibid, i, 185), and declares that he must be in some sense extended, and have some common property with the matter upon which he acts. It would seem, indeed, that God is rather matter of a different kind from the ordinary than in any strict sense immaterial.