For a super stripped down example, if someone from an Abrahamic Religion was asked whether or not they believe animals have souls, they'd probably answer "no." The logic might flow something like this.
An axiom is "a statement or proposition that is regarded as being established, accepted, or self-evidently true." If we both accept the axiom, we can both debate and discuss that which flows from the axiom. Important to note: there are no axioms in science. Nothing is assumed. And when debating with someone who doesn't hold the same axioms you do, shit falls apart real quick. Watch:
Man was created in God's image, so only man has a soul. Evidence of a soul is the ability to know, recognize, and come to God, and therefore exhibit Godly attributes like wisdom and knowledge. Humans are the only animals on the planets to embrace science and the arts to such a massive degree and this is proof God has given us souls. Therefore only humans have souls.
Axiom, so (false) axiom. Axiom, and therefore axiom. Biased observation therefore conclusion.
If you're buddhist, man isn't created in God's image. there's no reason to assume that image has anything to do with soul. Your definition of "soul" is proprietary therefore your definition of wisdom and knowledge are, too. "to such a massive degree" is a choice - if a chimp can get ants to climb on a stick we aren't the only tool makers and to wrap it all up in a "therefore only humans have souls" only serves to demonstrate how dependent on your framework your "reason" truly is.