The treatise "De l'Esprit" has for its object the setting forth of the doctrine of utility in its extreme form. As a preliminary argument all the operations of the mind are reduced to sensation. "When by a succession of my ideas, or by the vibration which certain sounds cause in the organ of my ears, I recall the image of an oak, then my interior organs must necessarily be nearly in the same situation as they were at the sight of that oak. Now this situation of the organs must necessarily produce a sensation; it is, therefore, evident that memory is sensation. "Having stated this principle, I say further that it is in the capacity which we have of perceiving the resemblances or the differences, the agreement or the disagreement, which different objects have with each other, that all the operations of the mind consist. Now this capacity is nothing else than physical sensibility; therefore everything is reduced to sensation." Utility, according to Helvetius, is the foundation of all our moral feelings. Each person praises as just in others only those actions which are useful to himself; every nation or society praises what is useful to it in its corporate capacity. "If a judge acquits a guilty man, if a minister of state promotes an unworthy one, each is just, according to the man protected. But if the judge punishes, or the minister refuses, they will always be unjust in the eyes of the criminal and of the unsuccessful."... "The Christians who justly spoke of the cruelties practiced on them by the pagans as barbarity and crime, did they not give the name of zeal to the cruelties which they, in their turn, practiced on these same pagans?" As the physical world is subject to laws of motion, so is the moral world to those of interest. All men alike strive after their own happiness. It is the diversity of passions and tastes, some of which are in accordance with the public interest and others in opposition to it, which form our virtues and our vices. We should, therefore, not despise the wicked, but pity them, and thank heaven that it has given us none of those tastes and passions which would have obliged us to seek our happiness in other people's misfortunes. This opinion, although extravagantly stated, was, as we have seen, but the caricature of the doctrine of utility, as taught by Locke and held by his followers.