thought in transferring the past to the future. Let any one try to
account for this operation of the mind upon any of the received systems
of philosophy, and he will be sensible of the difficulty. For my part, I
shall think it sufficient, if the present hints excite the curiosity of
philosophers, and make them sensible how defective all common theories
are in treating of such curious and such sublime subjects.



SECTION VII.

OF THE IDEA OF NECESSARY CONNEXION.

PART I.


48. The great advantage of the mathematical sciences above the moral
consists in this, that the ideas of the former, being sensible, are
always clear and determinate, the smallest distinction between them is
immediately perceptible, and the same terms are still expressive of the
same ideas, without ambiguity or variation. An oval is never mistaken
for a circle, nor an hyperbola for an ellipsis. The isosceles and
scalenum are distinguished by boundaries more exact than vice and
virtue, right and wrong. If any term be defined in geometry, the mind
readily, of itself, substitutes, on all occasions, the definition for
the term defined: Or even when no definition is employed, the object
itself may be presented to the senses, and by that means be steadily and
clearly apprehended. But the finer sentiments of the mind, the
operations of the understanding, the various agitations of the passions,
though really in themselves distinct, easily escape us, when surveyed by