Why, let us ask, does Mathematical truth occupy so lofty a position? Because, _first_, the constitution of our nature obliges us to accept its axioms, and by consequence each successive step in its impregnable demonstrations. _Next_, because we can verify so many of its theorems objectively. We apply them to remote planetary and stellar spheres beyond our own reach; where our own minds can neither alter nor colour anything. What then ought to be the fair and legitimate inference from an issue magnificently tried throughout the celestial universe? Surely this, and no other. It confirms, in the very highest possible degree, the truth-telling power of our own human nature. Whatsoever our mental constitution clearly compels us to accept, that same we ought to hold true, and maintain unswervingly. Henceforth, therefore, we ought to look upon our Reason as having been put upon its conclusive trial. Every year that passes renders the verdict if possible more triumphant. We ought, henceforth, to make our assent absolute and unhesitating in the case of those other truths, which, while things continue as they now are, can never be tried and confirmed by an appeal of the same description. It is not difficult to see how opposite would have been the issue from an employment of improper tests;--the test, for instance, of the _Unthinkable_. The universe, we should then have said, must be thought of as finite or as infinite. Either way it is inconceivable;--therefore the Universe cannot exist objectively at all.