Scottish metaphysician, born in Aberdeen and educated at Kings College. He maintained himself by acting as tutor to noblemens sons. From 1741 to 1747 he lived with Lord Blantyre and Mr. Hay of Drummelzier at Utrecht, and made excursions in Flanders, France and Germany. Returning to Scotland, he lived at Whittingehame, near Edinburgh, till his death in 1750. At Spa he had met John Wilkes, then twenty years of age, and formed a lasting friendship with him. His chief work, An Inquiry into the Nature of the Human Soul (editions 1733, 1737 and 1745; with appendix added in 1750 in answer to an attack in Maclaurins Account of Sir I. Newtons Philosophical Discoveries, and dedication to John Wilkes), examines the properties of matter. The one essential property of matter is its inactivity, vis inertiae (accepted later by Monboddo). All movement in matter is, therefore, caused by some immaterial force, namely, God. But the movements of the body are not analogous to the movements of matter; they are caused by a special immaterial force, the soul. The soul, as being immaterial, is immortal, and its consciousness does not depend upon its connection with the body. The argument is supported by an analysis of the phenomena of dreams, which are ascribed to direct spiritual influences. Lastly Baxter attempted to prove that matter is finite. His work is an attack on Tolands Letters to Serena (1704), which argued that motion is essential to matter, and on Locke and Berkeley. His criticism of Berkeley (in the second volume) is, however, based on the common misinterpretation of his theory (see Berkeley). Sir Leslie Stephen speaks of him as a curious example of the effects of an exploded metaphysics on a feeble though ingenious intellect.
Beside the Inquiry, Baxter wrote Matho sive Cosmotheoria Puerilis (an exposition in Latin of the elements of astronomy written for his pupilseditions in English 1740, 1745 and 1765, with one dialogue re-written); Evidence of Reason in Proof of the Immortality of the Soul (published posthumously from MSS. by Dr. Duncan in 1779).
See life in Biographia Britannica; McCoshs Scottish Philosophy, pp. 4249.