Besides preferring the learning of Arabian and other distant lands to the schools of Gaul, and favoring scientific investigation rather than unquestioning faith, Adelard also sets reason above authority. He not only complains of his generation’s inborn prejudice against new ideas, but later on, when his nephew proposes to turn his questions from the subject of plants to that of animals, enters upon a longer diatribe against scholastic reliance upon past authorities. “It is difficult for me to discuss animals with you. For I learned from my Arabian masters under the leading of reason; you, however, captivated by the appearance of authority, follow your halter. Since what else should authority be called than a halter? For just as brutes are led where one wills by a halter, so the authority of past writers leads not a few of you into danger, held and bound as you are by bestial credulity. Consequently some, usurping to themselves the name of authority, have used excessive license in writing, so that they have not hesitated to teach bestial men falsehood in place of truth. For why shouldn’t you fill rolls of parchment and write on both sides, when in this age you generally have auditors who demand no rational judgment but trust simply in the mention of an old title?”[52] Adelard adds that those who are now reckoned authorities gained credence in the first instance by following reason, asserts that authority alone is not enough to convince, and concludes with the ultimatum to his nephew: “Wherefore, if you want to hear anything more from me, give and take reason. For I’m not the sort of man that can be fed on a picture of a beefsteak.”[53] [Sidenote: Need of the telescope and microscope already felt.] The history of natural philosophy and science has demonstrated that the unaided human reason has not been equal to the solution of the problems of the natural universe, and that elaborate and extensive observation, experience, and measurement of the natural phenomena are essential. But exact scientific measurement was not possible with the unaided human senses and required the invention of scientific instruments. As Adelard says in _De eodem et diverso_, “The senses are reliable neither in respect to the greatest nor the smallest objects. Who has ever comprehended the space of the sky with the sense of sight?... Who has ever distinguished minute atoms with the eye?”[54] Notable natural questions these, showing that the need of the telescope and microscope was already felt and that the discovery must in due time follow! [Sidenote: Some quaint speculative science.]