A few years ago, an Inspector of Schools--a Mr. Jellinger Symonds--opening, perhaps for the first time, an elementary book on astronomy, came on something which he conceived to be a difficulty in the theory of lunar motion. His objection was on the face of it plausible. The true motions of the heavenly bodies are universally the opposite of the apparent motions. Mr. Symonds conceived that the moon could not revolve on its axis, because the same side of it was continually turned towards the earth; and because if it were connected with the earth by a rigid bar--which, as he thought, would deprive it of power of rotation--the relative aspects of the two bodies would remain unchanged. He sent his views to the 'Times.' He appealed to the common sense of the world, and common sense seemed to be on his side. The men of science were of course right; but a phenomenon, not entirely obvious, had been hitherto explained in language which the general reader could not readily comprehend. A few words of elucidation cleared up the confusion. We do not recollect whether Mr. Symonds was satisfied or not; but most of us who had before received what the men of science told us with an unintelligent and languid assent, were set thinking for ourselves, and, as a result of the discussion, exchanged a confused idea for a clear one. It was an excellent illustration of the true claims of authority and of the value of open enquiry. The ignorant man has not as good a right to his own opinion as the instructed man. The instructed man, however right he may be, must not deliver his conclusions as axioms, and merely insist that they are true. The one asks a question, the other answers it, and all of us are the better for the business. Now, let us suppose the same thing to have happened when the only reply to a difficulty was an appeal to the Astronomer-Royal, where the rotation of the moon was an article of salvation decreed by the law of the land, and where all persons admitted to hold office under the State were required to subscribe to it. The Astronomer-Royal--as it was, if we remember right, he was a little cross at Mr. Symond's presumption--would have brought an action against him in the Court of Arches; Mr. Symonds would have been deprived of his inspectorship--for, of course, he would have been obstinate in his heresy; the world outside would have had an antecedent presumption that truth lay with the man who was making sacrifices for it, and that there was little to be said in the way of argument for what could not stand without the help of the law. Everybody could understand the difficulty; not everybody would have taken the trouble to attend to the answer. Mr. Symonds would have been a Colenso, and a good many of us would have been convinced in our secret hearts that the moon as little turned on its axis as the drawing-room table.