Roger Bacon actually wanted the Pope to forbid the study of Aristotle because his works were leading men astray from the true study of science — his authority being looked upon as so great that men did not think for themselves, but accepted his assertions. Smaller men are always prone to act thus at any period in the world's history, and we undoubtedly in our time have a very large number who do not think for themselves, but swear on the word of some master or other, and very seldom so adequate a master as Aristotle.
Bacon insisted that the four great grounds of human ignorance are : " First, trust in inadequate authority; second, that force of custom which leads men to accept without properly questioning what has been accepted before their time; third, the placing of confidence in the assertions of the inexperienced; and fourth, the hiding of one's own ignorance behind the parade of superficial knowledge, so that we are afraid to say, 41 do not know.' " Prof. Henry Morley suggested that: " No part of that ground has yet been cut away from beneath the feet of students, although six centuries have passed. We still make sheep walks of second, third, and fourth, and fifth hand references to authority; still we are the slaves of habit, still we are found following too frequently the untaught crowd, still we flinch from the righteous and wholesome phrase, ' I do not know,' and acquiesce actively in the opinion of others that we know what we appear to know".
It used to be the custom to make little of the medieval scientists because of their reverence for Aristotle. Generations who knew little about Aristotle, especially those of the seventeenth and eighteenth centuries, were inclined to despise preceding generations who had thought so much of him. We have come to know more about Aristotle in our own time, however, and as a consequence have learned to appreciate better medieval respect for him. Very probably at the present moment there would be almost unanimous agreement of scholars in the opinion that Aristotle's was the greatest mind humanity has ever had. This is true not only because of his profound intellectual penetration, but above all because of the comprehensiveness of his intelligence. For depth and breadth of mental view on a multiplicity of subjects, Aristotle has never been excelled and has but very few rivals. The admiration of the Middle Ages for him, instead of being derogatory in any way to the judgment of the men of the time, or indicating any lack of critical appreciation, rather furnishes good reasons for high estimation of both these intellectual modes of the medieval mind. Proper appreciation of what is best is a much more difficult task than condemnation of what is less worthy of regard. It is the difference between constructive and destructive criticism. Medieval appreciation of Aristotle, then, constitutes rather a good reason for admiration of them than for depreciation of their critical faculty; and yet they never carried respect and reverence to unthinking worship, much less slavish adoration. Albertus Magnus, for instance, said: " Whoever believes that Aristotle was a God must also believe that he never erred; but if we believe that Aristotle was a man, then doubtless he was liable to err just as we are." We have a number of direct contradictions of Aristotle from Albert. A well-known one is that with regard to Aristotle's assertion that lunar rainbows appeared only twice in fifty years. Albert declared that he himself had seen two in a single year.
Galen, after Aristotle, was the author oftenest quoted in the Middle Ages, and most revered. Anyone who wants to understand this medieval reverence needs only to read Galen. There has probably never been a greater clinical observer in all the world than this Greek from Pergamos, whose works were destined to have so much influence for a millennium and a half after his time. How well he deserved this prestige only a careful study of his writings will reveal. It is simply marvellous what he had seen and writes about. Anatomy, physiology, pathological anatomy, diagnosis, therapeutics —all these were magnificently developed under his hands, and he has left a record of accurate and detailed observation. There are many absurdities easily to be seen in his writings now, but no one has yet written on medicine in any large way who has avoided absurdities, nor can anyone hope to, until we know much more of the medical sciences than at present. The therapeutics of any generation is always absurd to the second succeeding generation, it has been said. Those in the modern time who know their Galen best have almost as much admiration for him, in spite of all our advance in the knowledge of medicine, as the medieval people had. No wonder, seeing the depth and breadth of his knowledge, that he was thought so much of, and that men hesitated to contravene anything that he said.
Even in the authorities to which they turned with so much confidence, the medieval physicians are admirable. If man must depend on authority, then he could not have better than they had. As with regard to this, so in all other matters relating to the Middle Ages, the ordinarily accepted notions prove to have been founded on ignorance of actual details, and misconceptions as to the true significance of their point of view. To have contempt give way to admiration, we need only to know the realities even in such meagre details as can be given in a short manual of this kind. The thousand years of the Middle Ages are now seen to have been full of interesting and successful efforts in every mode of human activity, and medicine and surgery shared in this to the full.