Another vital consideration as to experiment, is that it should be kept impersonal. In most cases, if one is to experiment fruitfully and satisfactorily, there should be some special object in view, some particular point to be rejected or confirmed. Unless you know just what you are looking for, you are apt not to see. Again and again in Darwin’s book on Orchids, as in many of the others, we read that he made investigations and got no results, simply because he did not have in mind theoretical possibilities. When he had reasoned out what ought to happen or might happen, he often found that it did. The danger of this method is obvious. When the experimenter is so desperately anxious to see something, unless he is most carefully trained and disciplined, he will see it. It is not to be supposed that Darwin always escaped this danger, but few men have been more prepared for it or more ready to allow for it than he. His confession of prejudice, his recognition of the importance of certain points in his general theory and of his unwillingness to have anything interfere with them are among his greatest charms: ‘I remember well the time when the thought of the eye made me cold all over.... The sight of a feather in a peacock’s tail, whenever I gaze at it, makes me sick.’[469] We have already enlarged under observation on the essential quality of accuracy, and it may simply be added that accuracy is doubly important in all experiments for a theoretical purpose. Accuracy, complete, detailed, mathematical exactitude, was Darwin’s hobby, and the minuteness of his record constantly exemplifies it.