But some of you may ask, How can any theory of evolution guarantee that anything of the present shall survive in the future? It is continually changing and destroying former types. The old order of everything changes and passes away, giving place to the new. But is this the whole truth? Evolution is a radical process, but we must never forget that it is also, and at the same time, exceedingly conservative. The cell was the first invention of the animal kingdom, and all higher animals are and must be cellular in structure. Our tissues were formed ages on ages ago; they have all persisted. Most of our organs are as old as worms. All these are very old, older than the mountains, and yet I cannot doubt that they must last as long as man exists. Indeed, while Nature is wonderfully inventive of new structures, her conservatism in holding on to old ones is still more remarkable. In the ascending line of development she tries an experiment once exceedingly thorough, and then the question is solved for all time. For she always takes time enough to try the experiment exhaustively. It took ages to find how to build a spinal column or brain, but when the experiment was finished she had reason to be, and was, satisfied. And if this is true of bodily organs we should expect that the same law would hold good when the animal development gradually passes over into the spiritual. And what is human history but the record of moral and religious experiments, and their success or failure according as the experimenters conformed to the laws of the spiritual forces with which they had to do? We need not fear that our old fundamental beliefs will be lost. Their very age shows that they have been thoroughly tested in the great experiment of human history and found sure. Modified they may be; they will be used for higher purposes and the building of better characters than ours. They will not be lost or discarded. We too often think of nature as building like man, with huge scaffoldings, which must later be torn down and destroyed. But in the forest the only scaffolding is the heart of oak.