This post is pretty confused and under researched.
Firstly, there seems to be a confusion about the topic: are we talking about definitions or syllogisms? No one (certainly not Aristotle) will claim that definitions, or anything of the form “All humans are mortal” is logically valid. Only inferences can be valid, and definitions are not inferences.
Secondly, there seems to be a confusion between logical validity and truth. No one has ever claimed that the validity of a syllogism can lend certainty or even support any given empirical claim. If the claim is the conclusion of a valid syllogism containing true premises, then it must be true, but it is not empirical. And the question of its certainty rests entirely on our certainty of the premises.
Lastly, whatever claims this post makes about Aristotle or people ‘of Aristotle’s time’ seem to be pretty unfounded. Aristotle’s views on logic, definitions, and necessity are pretty complex, and nothing of them is represented here. Aristotle certainly didn’t believe that everything falling under a definition has every attribute described in that definition. Aristotle’s definition for human being was probably “rational animal” and he did not think every human being was rational.
This post is pretty confused and under researched.
Firstly, there seems to be a confusion about the topic: are we talking about definitions or syllogisms? No one (certainly not Aristotle) will claim that definitions, or anything of the form “All humans are mortal” is logically valid. Only inferences can be valid, and definitions are not inferences.
Secondly, there seems to be a confusion between logical validity and truth. No one has ever claimed that the validity of a syllogism can lend certainty or even support any given empirical claim. If the claim is the conclusion of a valid syllogism containing true premises, then it must be true, but it is not empirical. And the question of its certainty rests entirely on our certainty of the premises.
Lastly, whatever claims this post makes about Aristotle or people ‘of Aristotle’s time’ seem to be pretty unfounded. Aristotle’s views on logic, definitions, and necessity are pretty complex, and nothing of them is represented here. Aristotle certainly didn’t believe that everything falling under a definition has every attribute described in that definition. Aristotle’s definition for human being was probably “rational animal” and he did not think every human being was rational.