They intimate, in no ambiguous terms, not only that Catholicism is effete, and Christianity itself dead or dying, but that Theology of every kind, even the simplest and purest form of Theism, must speedily vanish from the earth.

Admitting that the religious element was necessarily developed in the infancy of the species, and that its influence was alike inevitable and salutary during the world's minority, when it was placed provisionally "under tutors and governors," they proclaim that mankind have outgrown the vestments which suited them in earlier times, and that now they must "put away childish things." That such sentiments have been publicly avowed, that they have been proclaimed as the scientific results of speculative thought, and that they have been widely circulated in the vehicles both of philosophic discussion and of popular literature, will be proved by evidence, equally sad and conclusive, in the succeeding chapters; in the meantime we refer to them merely for the purpose of showing that, in so far as their influence prevails, they must necessarily tend, unless they be counteracted by some effective antidote, to generate such a prejudice against the whole scheme of Theology, whether Natural or Revealed, as may be expected, especially in the case of young, inexperienced, and ardent minds, to prevent them from entertaining the subject at all, or examining, with serious and candid interest, any kind or amount of evidence that might be adduced in regard to it.

For this reason, we propose to review the various Theories or Systems which may be said to embody and exhibit these prevailing tendencies, to meet our opponents on their own chosen ground, and to subject their favorite speculations to a rigorous and sifting scrutiny; and this, not for the purpose of proving our fundamental position, for that must rest on its proper and independent evidence, but simply with the view of neutralizing the adverse presumptions which prevent many from considering its claims, and proving that it is a subject that demands and deserves their serious and sustained attention.
Taking a comprehensive view of European Science and Literature during the last half century, we may discern the great currents, or chief tendencies, of speculative thought, in so far as it bears on the evidences and doctrines of Religion, in several distinct but closely related systems of opinion, which, whether considered severally or collectively, must exert, in proportion to their prevalence, a powerful influence on the side of Atheism.

These systems may be divided generally into _two_ great classes, according as they relate to the _substance_ or to the _evidence_ of Theism, to the _truths_ which it involves, or the _proofs_ to which it appeals.

The interval between the first and second French Revolutions may be regarded as the season during which the theories to which we refer were progressively developed, and ultimately consolidated in their existing forms.