Aristotle was a student of Plato's and greatly admired his teacher. However as his own philosophical inquiries progressed he began to question the wisdom of his teacher, wrestling with this and eventually coming to terms with it, he wrote "Plato is dear to me, but dearer still is the truth"

For centuries after the age of the classical philosophers most of western civilization had embraced Aristotle's ideas about reality entirely uncritically, while embracing most of Plato's ideas about knowledge and religion. The Dark ages were characterized by an uncritical acceptance of the teachings of the ancients, where for nearly 1500 years virtually no advancements were made and all questions about reality were directed toward the ancient texts.

Aristotle would have never welcomed this, his own writings are full of deep sense of inquiry and his own opinions changed on many topics as he investigated them further. Aristotle's deeply inquisitive nature is evidenced by his love for collecting and analyzing animals, attributing characteristics to them and classifying them - the entire science of Taxonomy was primarily founded by Aristotle, as well as the rules for describing nature accurately in the what we today refer to as Aristotlean logic. But on some matters his speculations were wrong, and the uncritical acceptance of these for centuries hindered further progress.

The Roman doctor Galen, who did in fact proclaim to have figured everything out in medicine, was also uncritically accepted throughout the Dark Ages, he is the origin of blood letting and disease coming from an imbalance in the various 'humours' (fluids in the body) today some words are historical descendants of his medical quackery, such as being sanguine.

The middle ages did cultivate an atmosphere of inquiry and questioning, but it was entirely focused on theological matters that had little relevance to material progress on earth, and it was only when that questioning attitude was shifted toward descriptions of reality that the renaissance and scientific revolutions would begin. One great admirer of Aristotle was Isaac Newton. And one incorrect teaching of Aristotle's was that objects need to be perpetually pushed in order to keep moving, but Newton's understanding of nature was making it obvious to him that some things keep moving - even forever - without slowing down and in fact something else has to push on them to slow them. This today is his first law of motion and the notion we readily recognize as inertia, but the fact that he was proposing something that contradicted Aristotle greatly disturbed him.

Wrestling with this, he finally came to terms with it from Aristotle's own famous quote about Plato. Paraphrasing Aristotle and illustrating both his admiration for Aristotle and accepting that he had moved beyond Aristotle's teaching, Isaac Newton wrote in the margin of one of his notebooks "Aristotle is dear to me, but dearer still is the truth"