Psychology, or the science of the human mind, teaches a very different doctrine. According to this science, the perception of matter is a secondary and composite truth. It admits of being analysed into a subjective and an objective element--a mental modification called perception on the one hand, and matter _per se_ on the other. It is an effect induced by real objects. It is not the first _datum_ of intelligence. It has matter itself for its antecedent. Such, in very general terms, is the explanation of the perception of matter which psychology proposes. Psychology and metaphysics are thus radically opposed to each other in their solutions of the highest problem of speculation. Stated concisely, the difference between them is this:--psychology regards the perception of matter as susceptible of analytic treatment, and travels, or endeavours to travel, beyond the given fact: metaphysic stops short in the given fact, and there makes a stand, declaring it to be all indissoluble unity. Psychology holds her analysis to be an analysis of things. Metaphysic holds the psychological analysis to be an analysis of sounds--and nothing more. These observations exhibit, in their loftiest generalisation, the two counter doctrines on the subject of perception. We now propose to follow them into their details, for the purpose both of eliciting the truth and of arriving at a correct judgment in regard to the reformation which Dr Reid is supposed to have effected in this department of philosophy. The psychological or analytic doctrine is the first which we shall discuss, on account of its connexion with the investigations of Dr Reid,--in regard to whom we may state, beforehand, our conclusion and its grounds, which are these:--that Reid broke down in his philosophy, both polemical and positive, because he assumed the psychological and not the metaphysical doctrine of perception as the basis of his arguments. He did not regard the perception of matter as absolutely primary and simple; but in common with all psychologists, he conceived that it admitted of being resolved into a mental condition, and a material reality; and the consequence was, that he fell into the very errors which it was the professed business of his life to denounce and exterminate. How this catastrophe came about we shall endeavour shortly to explain.