At the age of seventy-one, Thomas Reid resigned from his University of Glasgow professorship to prepare for publication his celebrated classroom lectures on mental and moral philosophy. The intellectual world already knew the general thrust of the new Scottish Realism through his Inquiry into the Human Mind on the Principles of Common Sense (1764); however, the full articulation and defense of the system awaited the appearance of his two books of essays, works so lucid and so plausible that they became almost at once the basis of the orthodox philosophy of the English-speaking world. Reid’s philosophy is everything that a “public philosophy” should be. Although it lacks the graceful style of certain eighteenth century philosophers, it has a masculine strength and a directness that still arouses admiration.
Essays on the Intellectual Powers of Man contains eight essays of rather unequal length, each (except the Introduction) concerning one of humankind’s intellectual powers or faculties. It is characteristic of Reid’s philosophy that, like those of Joseph Butler and Francis Hutcheson, it makes no effort to reduce the different activities to a common denominator. Sense perception, memory, conception (imagination), abstraction, judgment, reason, and taste are so many distinct and irreducible activities, although they may also occur in combination. Reid begins each essay by identifying the power in question and explaining its typical features. There follows a historical account telling how other philosophers have dealt with the subject. Often, in addition, one of the British empiricists is selected for quotation and detailed refutation—not the least profitable part of the work.
Reid was a conscientious empiricist, pledged to carry out the program of English philosopher Francis Bacon for the mental and moral sciences. By observation and investigation, he hoped to arrive at fundamental laws comparable to those that English physicist Isaac Newton had found in natural philosophy. His method is basically introspective: One can learn to attend to one’s own mental activities, describe them, and relate them to one another. In this manner, people can map out the “human constitution.” Description, however, is all that humanity can attain, because humankind is not given to know the causes of things. In fact, with Reid, as with most of his contemporaries, the underlying assumption (as basic to them as evolution was to the late nineteenth century) was that by a perfect wisdom, all the parts of the world are adjusted to one another.
In addition to his appeals to introspection, Reid makes frequent appeal to common speech to support what he takes to be the witness of humanity’s constitution. An example is this: Is beauty properly said to be an emotion in the mind of the perceiver, or a property of the object viewed? Language witnesses the latter. Are heat, hardness, and the like perceived as ideas in the mind or as qualities in bodies? People’s speech testifies that they are perceived as qualities.
Reid’s attitude toward the history of philosophy (which he regarded as the history of error) is central to his own “common sense” point of view. He shared the optimism of the eighteenth century, which held that the truth is always near at hand and that the first step toward enlightening humankind is to clear away ignorance, prejudice, and artificiality. In Reid’s view, all the complications in mental philosophy stem from the very old error of thinking of the mind after the analogy of body. People observe that, in the physical world, there is no action at a distance, and they suppose that similarly the mind can act and be acted on only by what is immediately present to it. The ancient philosophers taught that bodies give off films that, passing through the sense organs, leave impressions on the mind. The moderns, following French philosopher René Descartes, refined their doctrine and retained the old “phantasms” under the new name of...
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