ABSTRACT
The postulates and axioms prefacing our expositions of exact science—our works on Geometry and our Mechanical Treatises—are received on the direct warrant of consciousness that they are indisputable. Similarly with all that we regard as objective truths; whether known immediately by simple intuitions, or mediately by the series of intuitions constituting a deductive argument. If Psychology is ever to become anything more than a mere aggregation of opinions, it can only be by the establishment of some datum universally agreed to. The inability to come to any agreement respecting the first principles of things, affords in itself ample ground for thinking that there exists some yet unestablished datum of human knowledge, which must be found before the endless disputes can be brought to an end. But the need for a datum is most clearly seen on contemplating the efforts made to overthrow the unnatural systems.
