Adversaries are almost all Materialists, Sensists, and Associationists, who refuse to acknowledge the essential difference between the intellect and sense. Philosophers akin to Sensism are John Locke (1632), E. B. De Condillac (1715-1780), Alexander Bain (1818-1903), Herbert Spencer (1820-1903), J. P. Herbart (1776-1841), John Stuart Mill (1806-1873) and H. Taine (1828-1893). They explain all intellectual functions either by outright denial, or by contending that they are simply the simple association of images.⁶ Associationalism promoted by David Hume (1711-1776) is an outmoded form of Sensism which is concerned almost wholly to explain knowledge by way of association of images, or images and sensations.⁷ In America, Associationalism was called Structuralism. The Gestalt psychologists who opposed Assoicationalism are also Sensists.⁸

Other adversaries are Spiritists and Theosophists, and all who believe in the transmigration of souls or reincarnation.

Adversaries are found among many Evolutionists, especially Darwinists, and all those who assert the origin of the human species from some species of animal.⁹

Adversaries are found among some experimental psychologists, especially promoters of the experiments of W. Köhler. Also in this group would be J. F. Ebbinghaus (1850-1009) and W.Wundt (1832-1921).¹⁰

Adversaries like Pythagoras, Axaxagoras, the Platonists, the Neo-Platonists, and especially Porphyrius, Montaigne, and Flourens have maintained that beasts have rational souls.¹¹

Proponents of the thesis are all the Scholastics following Aristotle, Christian philosophers, the Neo-Scholastics, and even many experimental psychologists.¹² Aristotle and Aquinas represent the natural world of living organisms as a graduated scale ascending from less to more perfect forms of life. "Aquinas sees the graduated scale as involving essential differences," notes Adler.¹³ Proponents of the thesis are such Neo-Scholastics as Palmes,¹⁴ Klubertanz¹⁵ and La Vecchia.¹⁶

Adversaries who reject the proposal make it clear that the thesis proposed is a serious subject for discussion. The thesis proposed and defended as true presents an objective problem worthy of dialogue.

Adversaries who seriously contradict the proposal in this chapter deserve respect. These adversaries have reasons for their position. In every false position there is some truth. In dialogue, every attempt should be made to clarify that truth. In this case, instinct on the part of animals directs them to the more complicated and more wonderful activities.¹⁷ Further, the question is complicated because man himself is partly animal.¹⁸ Accordingly, even if our proposal and its proofs demonstrate the adversaries wrong, their reasoning can be understood and respected.