The theme of the Treatise on the Sensations, 1754, is: Memory, comparison, judgment, abstraction, and reflection (in a word, cognition) are nothing but different forms of attention; similarly the emotions, the appetites, and the will, nothing but modifications of desire; while both alike take their origin in sensation. Sensation is the sole source and the sole content of the life of the mind as a whole. To prove these positions Condillac makes use of the fiction of a statue, in which one sense awakes after another, first the lowest of the senses, smell, and last the most valuable, the sense of touch, which compels us (by its perception of density or resistance) to project our sensations, and thus wakes in us the idea of an external world. In themselves sensations are merely subjective states, modes of our own being; without the sense of touch we would ascribe odor, sound, and color to ourselves. Condillac distinguishes between sensation and ideas in a twofold sense, as mere ideas (the memory or imagination of something not present), and as ideas of objective things (the image, representative of a body); this latter sense is meant when he says, touch sensations only are also ideas.
For the details of the deduction, which often makes very happy use of a rich store of psychological material, the reader must be referred to the more extended expositions. Here we can only cite as examples the chief among the genetic definitions. Perceptions (impressions) and consciousness are the same thing under different names. A lively sensation, in which the mind is entirely occupied, becomes attention, without the necessity of assuming an additional special faculty in the mind. Attention, by its retentive effect on the sensation, becomes memory. Double attention—to a new sensation, and to the lingering trace of the previous one—is comparison; the recognition of a relation (resemblance or difference) between two ideas is judgment; the separation of an idea from another naturally connected with it, by the aid of voluntary linguistic symbols, is abstraction; a series of judgments is reflection; and the sum total of inner phenomena, that wherein ideas succeed one another, the ego or person. All truths concern relations among ideas. The tactual idea of solidity accustoms us to project the sensations of the other senses also, to transfer them thither where they are not; hence arise the ideas of our body, of external objects, and of space. If we perceive several such projected qualities together, we refer them to a substratum—substance, which we know to exist, although not what it is. By force we mean the unknown, but indubitably existent, cause of motion.
There are no indifferent mental states; every sensation is accompanied by pleasure or pain. Joy and pain give the determining law for the operation of our faculties. The soul dwells longer on agreeable sensations; without interest, ideas would pass away like shadows. The remembrance of past impressions more agreeable than the present ones is need; from this springs desire (désir) then the emotions of love, hate, hope, fear, and astonishment; finally, the will as an unconditional desire accompanied by the thought of its possible fulfillment. All inclinations, good and bad alike, spring from self-love. The predicates "good" and "beautiful" denote the pleasure-giving qualities of things, the former, that which is agreeable to smell and taste (and the passions), the latter, that which pleases sight, hearing, feeling (and the intellect). Morality is the conformity of our actions to laws, which men have established by convention with mutual obligations. In this way the good, which at first was the servant of the passions, becomes their lord.
Man's superiority to the brute depends on the greater perfection of his sense of touch; on the greater variety of his wants and his associations of ideas; on the idea of death, which leads him to seek not merely the avoidance of pain but also self-preservation; and the possession of language. Without denomination no abstractions, no thought, no handing down of knowledge. Although all that is mental has its origin, in the last analysis, in simple sensations, its development requires emancipation from the sensuous, and language is the means for freeing ourselves from the pressure of sensations by the generalization and combination of ideas.
A more moderate representative of sensationalism was Charles Bonnet, who later exercised a considerable influence in Germany, especially until Tetens (1720-93; Essay in Psychology, or Considerations on the Operations of the Soul, 1755; Analytical Essay on the Faculties of the Soul, 1760; Philosophical Palingenesis, or Ideas on the Past and the Future of Living Beings, 1769, including a defense of Christianity; Collected Works, 1779). Sensations, to which he, too, reduces all mental life, are, in his view, reactions of the immaterial soul to sense stimuli, which operate merely as occasional causes. On the other hand, he emphasizes more strongly than Condillac the dependence of psychical phenomena on physiological conditions, and endeavors to show definite brain vibrations as the basis not only of habit, memory, and the association of ideas, but also of the higher mental operations. In harmony with these views he adheres to determinism, and finds the motive of all endeavor: in self-love, and its ultimate aim in happiness. To the latter the hope of immortality is indispensable. The link between Bonnet's theory of the thoroughgoing dependence of the soul on the body and his orthodox convictions, is formed by his idea of an imperishable ethereal body, which enables the soul in the life to come to remember its life on earth and, after the dissolution of the present material body, to acquire a new one. Animals as well as men share in the continuance of existence and the transition to a higher stage.
The material earnestness of these thinkers is in sharp contrast to the superficial and frivolous manner in which Helvetius (1715-71) carries out sensationalism in the sphere of ethics. His chief work, On Mind, came out in 1758; and a year after his death, the work On Man, his Intellectual Faculties and his Education. The search for pleasure or self-love is, as Helvetius thinks he has discovered for the first time,[1] the only motive of action; the laws of interest reign in the moral world as the laws of motion in the physical world; justice and love for our neighbors are based on utility; we seek friends in order to be amused, aided, and, in misfortune, compassionated by them; the philanthropist and the monster both seek only their own pleasure.
[Footnote 1: In reality not only English moralists, but also some among his countrymen, had anticipated him in the position that all actions proceed from selfishness, and that virtue is merely a refined egoism. Thus La Rochefoucauld in his Maxims (Réflexions, ou Sentences et Maximes Morales, 1665), La Bruyère (Les Charactères et les Moeurs de ce Siécle, 1687), and La Mettrie (of. pp, 251-253).]
Helvetius draws the proof for these positions from Condillac. Recollection and judgment are sensation. The soul is originally nothing more than the capacity for sensation; it receives the stimulus to its development from self-love, i.e., from powerful passions such as the love of fame, on the one hand, and, on the other, from hatred of ennui, which induces man to overcome the indolence natural to him and to submit himself to the irksome effort of attention—without passion he would remain stupid. The sum of ideas collected in him is called intellect. All distinctions among men are acquired, and concern the intellect only, not the soul: that which is innate—sensibility and self-love—is the same in all; differences arise only through external circumstances, through education. Man is the pupil of all that environs him, of his situation and his chance experience. The most important instrument in education is the law; the function of the lawgiver is to connect public and personal welfare by means of rewards and punishments, and thus to elevate morality. A man is called virtuous when his stronger passions harmonize with the general interest. Unfortunately the virtues of prejudice, which do not contribute to the public good, are more honored among most nations than the political virtues, to which alone real merit belongs. And self-interest is always the one motive to just and generous action; we serve only our own interests in furthering the welfare of the community. As the promulgator of these doctrines was himself a kind and generous man, Rousseau could make to him the apt reply: You endeavor in vain to degrade yourself below your own level; your spirit gives evidence against your principles; your benevolent heart discredits your doctrines.
The morality of enlightened self-love or "intelligent self-interest" appears in a milder form in Maupertuis (Works, 1752), and Frederick the Great,[1] to the latter of whom D'Alembert objected by letter that interest could never generate the sense of duty and reverence for the law.
[Footnote 1: Essay on Self-love as a Principle of Morals, 1770, printed in the proceedings of the Academy of Sciences. Cf. on Frederick, Ed. Zeller, 1886.]