tellect, and not the notice of the figure by the senses, that conducts the steps in the solution of theorems. No hand can describe the circle of which the intellect determines the properties. The real circle is in the mind of the geometrician, for the sensible one does not answer his purpose. Figures and symbols in mathematics, are expedients to assist the memory. The intellect alone produces all the magnificent results of this science.
It is usual to regard that knowledge which is to disclose the economy of nature, as incapable of attaining to the certainty of abstract science. But this view should not be taken, until it is proved that the intellect has been allowed the full exercise of its powers upon the subject. That this department of knowledge may be carried to absolute certainty, is shewn in the perfection to which the natural philosophy of the solar system has been brought; manifested
