It has been my privilege for some years to address regularly two very different audiences on two very different themes. On week days I have lectured to a class of students on the Natural Sciences, and on Sundays to an audience consisting for the most part of working men on subjects of a moral and religious character. I cannot say that this collocation ever appeared as a difficulty to myself, but to certain of my friends it was more than a problem. It was solved to me, however, at first, by what then seemed the necessities of the case--I must keep the two departments entirely by themselves. They lay at opposite poles of thought; and for a time I succeeded in keeping the Science and the Religion shut off from one another in two separate compartments of my mind. But gradually the wall of partition showed symptoms of giving way. The two fountains of knowledge also slowly began to overflow, and finally their waters met and mingled. The great change was in the compartment which held the Religion. It was not that the well there was dried; still less that the fermenting waters were washed away by the flood of Science. The actual contents remained the same. But the crystals of former doctrine were dissolved; and as they precipitated themselves once more in definite forms, I observed that the Crystalline System was changed. New channels also for outward expression opened, and some of the old closed up; and I found the truth running out to my audience on the Sundays by the week-day outlets. In other words, the subject-matter Religion had taken on the method of expression of Science, and I discovered myself enunciating Spiritual Law in the exact terms of Biology and Physics. Now this was not simply a scientific coloring given to Religion, the mere freshening of the theological air with natural facts and illustrations. It was an entire re-casting of truth. And when I came seriously to consider what it involved, I saw, or seemed to see, that it meant essentially the introduction of Natural Law into the Spiritual World. It was not, I repeat, that new and detailed analogies of _Phenomena_ rose into view--although material for Parable lies unnoticed and unused on the field of recent Science in inexhaustible profusion. But Law has a still grander function to discharge toward Religion than Parable. There is a deeper unity between the two Kingdoms than the analogy of their Phenomena--a unity which the poet's vision, more quick than the theologian's, has already dimly seen:-- "And verily many thinkers of this age, Aye, many Christian teachers, half in heaven, Are wrong in just my sense, who understood Our natural world too insularly, as if No spiritual counterpart completed it, Consummating its meaning, rounding all To justice and perfection, _line by line, Form by form, nothing single nor alone_, The great below clenched by the great above."[1]