Astronomers had long contented themselves with proving, from the
phaenomena, the true motions, order, and magnitude of the heavenly
bodies: Till a philosopher, at last, arose, who seems, from the happiest
reasoning, to have also determined the laws and forces, by which the
revolutions of the planets are governed and directed. The like has been
performed with regard to other parts of nature. And there is no reason
to despair of equal success in our enquiries concerning the mental
powers and economy, if prosecuted with equal capacity and caution. It is
probable, that one operation and principle of the mind depends on
another; which, again, may be resolved into one more general and
universal: And how far these researches may possibly be carried, it will
be difficult for us, before, or even after, a careful trial, exactly to
determine. This is certain, that attempts of this kind are every day
made even by those who philosophize the most negligently: And nothing
can be more requisite than to enter upon the enterprize with thorough
care and attention; that, if it lie within the compass of human
understanding, it may at last be happily achieved; if not, it may,
however, be rejected with some confidence and security. This last
conclusion, surely, is not desirable; nor ought it to be embraced too
rashly. For how much must we diminish from the beauty and value of this
species of philosophy, upon such a supposition? Moralists have hitherto
been accustomed, when they considered the vast multitude and diversity
of those actions that excite our approbation or dislike, to search for
some common principle, on which this variety of sentiments might depend.
And though they have sometimes carried the matter too far, by their
passion for some one general principle; it must, however, be confessed,
that they are excusable in expecting to find some general principles,
into which all the vices and virtues were justly to be resolved. The
like has been the endeavour of critics, logicians, and even politicians:
Nor have their attempts been wholly unsuccessful; though perhaps longer