Not so; because one habit has been formed and registered in the brain is no reason at all why another and contrary habit should not be formed and registered in its turn. To-day is the day of salvation, physically speaking, because a habit is a thing of _now_; it may be begun in a moment, formed in a month, confirmed in three months, become the character, the very man, in a year. There is growth to the new thoughts in a new tract of the brain, and “One custom overcometh another.” Here is the _natural_ preparation for salvation. The words are very old, the words of Thomas à Kempis, but the perception that they have a literal physical meaning has been reserved for us to-day. Only one train of ideas can be active at one time; the old cell connections are broken, and benign nature is busy building up the waste places, even be they the waste places of many generations. NO ROAD is set up in the track where the unholy thoughts carried on their busy traffic. New tissue is formed; the wound is healed, and, save, perhaps, for a scar, some little tenderness, that place is whole and sound as the rest. This is how one custom overcometh another: there is no conflict, no contention, no persuasion. Secure for the new idea a weighty introduction, and it will accomplish all the rest for itself. It will feed and grow; it will increase and multiply; it will run its course of its own accord; will issue in that current of automatic unconscious involuntary thought of the man which shapes his character. Behold, a new man! Ye must be born again, we are told; and we say, with a sense of superior knowledge of the laws of nature, How can a man be born again? Can he enter the second time into his mother’s womb and be born? This would be a miracle, and we have satisfied ourselves that “miracles do not happen.” And now, at last, the miracle of conversion is made plain to our dull understanding. We perceive that conversion, however sudden, is no miracle at all--using the word _miracle_ to describe that which takes place in opposition to natural law. On the contrary, we find that every man carries in his physical substance the gospel of perpetual, or of always possible, renovation; and we find how, from the beginning, Nature was prepared with her response to the demand of Grace. Is conversion possible? we ask; and the answer is, that it is, so to speak, a function for which there is latent provision in our physical constitution, to be called forth by the touch of a potent idea. Truly, His commandment is exceeding broad, and grows broader day by day with each new revelation of Science.