were what suggested to Laplace his system of the world. With the uncommon sense of a mathematician he perceived that such accordances were not necessitated by the law of gravitation, and on the other hand, could not be due to chance. The laws of probability showed millions to one against it. One of these happy harmonies was that all the large planets revolved about the Sun in substantially the same plane; another that they all travelled in the same sense (direction). Had they been unrelated bodies at the start, such agreement in motion was mathematically impossible. Their present consensus implied a common origin for all. In other words, the solar system must have grown to be what it is, not started so.
This basic fact we may consider certain. But from it we would fain go on to find out how it evolved. To do so the same process must be followed. Considering, then, our solar system from this point of view, one cannot but be struck by some further congruities it presents. These are not quite those that inspired Laplace, because of discoveries since, and demand in consequence a theory different from his.
The out about constructing a theory is that fresh facts will come along and knock for admission after the door is shut. They prove irreconcilables because they were not consulted in advance. The consequence is that since Laplace's time new relations have
