This fact is not only analogous to other psychical facts of less importance, such as that of sensory perception in relation to attention; it is also analogous to the spiritual facts which are so well known in the field of religion. In vain will a fact, however remarkable, be explained or even _demonstrated_ where there is no _faith_; it is not evidence but faith which opens the mind to truth. The very senses are useless as a medium if the internal activity does not open the doors to receive it. When the most striking miracles of Christ are related in the gospel, the narrative always concludes with: "And _many_ of those who saw, believed." The parable of the invitation to the feast, to which those who were absorbed in their own affairs could not respond, seems to indicate a fact similar to this intellectual fact, that the "preoccupations" of complicated pre-existing ideas prevent the new and obvious truth that presents itself, from entering in. It is for this reason that we need the Precursor to make ready for the Messiah. And for this reason the Messiah, and also new ideas, are readily received by the "simple," by those who are not "laden with heavy preoccupations," but have preserved the natural characteristics of the spirit: to be pure and always "expectant." When in 1628 Harvey discovered the circulation of the blood, physiology was almost unknown, and medicine was in the full tide of empiricism. It is well known that the Faculty of Medicine of Paris refused to believe in circulation, in _spite of_ experiments, and that it persecuted and calumniated Harvey. "That which pleases me in my son," said Diafoirus, "and in which he follows my example, is, that he remains faithful to the opinions of our ancient teachers, and that he has always refused either to _understand_ or to _listen_ to the arguments and experiments of the pretended discoveries of our century, especially as regards the circulation of the blood." * * * * *