I believe it scarce will be asserted, that the first species of reasoning alone is ever the cause of any action.

As its proper province is the world of ideas, and as the will always places us in that of realities, demonstration and volition seem, upon that account, to be totally removed, from each other.

Mathematics, indeed, are useful in all mechanical operations, and arithmetic in almost every art and profession: But it is not of themselves they have any influence: Mechanics are the art of regulating the motions of bodies to some designed end or purpose; and the reason why we employ arithmetic in fixing the proportions of numbers, is only that we may discover the proportions of their influence and operation.

A merchant is desirous of knowing the sum total of his accounts with any person: Why?
but that he may learn what sum will have the same effects in paying his debt, and going to market, as all the particular articles taken together.

Abstract or demonstrative reasoning, therefore, never influences any of our actions, but only as it directs our judgment concerning causes and effects; which leads us to the second operation of the understanding.
It is obvious, that when we have the prospect of pain or pleasure from any object, we feel a consequent emotion of aversion or propensity, and are carryed to avoid or embrace what will give us this uneasines or satisfaction.