Nevertheless a scientific examination of the foundations and truths of faith is allowed and wholesome. Nearly all the theological works written by Catholics since the days of _Justin_ and _Augustine_ are nothing but examinations of this kind. At every examination one proceeds with doubt and question. This is admitted; but this doubt must be merely a methodical one, not a serious one, nor need it be serious. These two kinds of doubt must be clearly distinguished. In case of a serious doubt I look upon the matter as really dubious, and withhold my assent. I am not yet convinced of its truth. This kind of a doubt is not allowed in matters of faith and it is the only one that is forbidden. In case of a methodical doubt I proceed as convinced of a truth, but I do not yet see the reasons plainly, and would like to be fully conscious of them. Evidently there is no need of casting aside the convictions I have hitherto held, and of beginning to think that the matter is by no means positively established. For instance, I am convinced that a complicated order must be the work of intellect; however, I would like to find the proof of it. Hence I proceed as if the truth were yet to be found. But it would evidently be absurd to think in the meantime that such admirable order could be the result of blind accident. Or, I am convinced that there must be a source for every event: I desire to find the demonstration of it. In the meantime shall I think it possible for another Nova Persei to be produced in the sky without any cause? Or, investigating to see whether I am capable of recognizing the truth, shall I seriously become a sceptic till I am convinced that I ought not to be such? As soon as I really doubt that I can recognize anything at all as true, obviously I cannot proceed any further. _Kant_ begins his “Critique of Pure Reason” with this doubt, and many imitate him, but only by evident inconsistency are they able to continue their researches by means of reason. Scientific examination does not consist in repudiating a certainty held hitherto, in order to arrive at it anew; it consists in bringing to one’s clear consciousness the reasons for that certainty, and in trying to formulate those reasons precisely. To investigate the light it is evidently not necessary first to extinguish it. Thus the believing Christian may most certainly probe into his religious conviction without interfering with his adherence, and by doing so proceed unprepossessed in the fullest sense, for unprepossession does not mean the rooting up of all certainty. At the threshold of wisdom does not sit Scepticism. What Unprepossession is Not. But the deeper, modern meaning of unprepossession is precisely the right to doubt seriously everything, especially the truths of the Christian faith; this is the freedom demanded. Scepticism, the stamp of our time.