Yet I think that if there is one purpose among possibly many which the builders of the pyramids had in their thoughts, which can be unmistakably inferred from the pyramids themselves, independently of all traditions, it is the purpose of constructing edifices which should enable men to observe the heavenly bodies in some way not otherwise obtainable. If the orienting of the faces of the pyramids had been effected in some such way as the orienting of most of our cathedrals and churches--_i.e._, in a manner quite sufficiently exact as tested by ordinary observation, but not capable of bearing astronomical tests,--it might reasonably enough be inferred that having to erect square buildings for any purpose whatever, men were likely enough to set them four-square to the cardinal points, and that, therefore, no stress whatever can be laid on this feature of the pyramids' construction. But when we find that the orienting of the pyramids has been effected with extreme care, that in the case of the great pyramid, which is the typical edifice of this kind, the orienting bears well the closest astronomical scrutiny, we cannot doubt that this feature indicates an astronomical purpose as surely as it indicates the use of astronomical methods. But while we thus start with what is to some degree an assumption, with what at any rate is not based on _à priori_ considerations, yet manifestly we may expect to find evidence as we proceed which shall either strengthen our opinion on this point, or show it to be unsound. We are going to make this astronomical purpose the starting-point for a series of _à priori_ considerations, each to be tested by whatever direct evidence may be available; and it is practically certain that if we have thus started in an entirely wrong direction, we shall before long find out our mistake. At least we shall do so, if we start with the desire to find out as much of the truth as we can, and not with the determination to see only those facts which point in the direction along which we have set out, overlooking any which seem to point in a different direction. We need not necessarily be in the wrong track because of such seeming indications. If we are on the right track, we shall see things more clearly as we proceed; and it may be that evidence which at first seems to accord ill with the idea that we are progressing towards the truth, may be found among the most satisfactory evidence obtainable. But we must in any case note such evidence, even at the time when it seems to suggest that we are on the wrong track. We may push on, nevertheless, to see how such evidence appears a little later. But we must by no means forget its existence. So only can we hope to reach the truth or a portion of the truth, instead of merely making out a good case for some particular theory.