Why do we use an article for "the mind," "the heart," or "the soul"? [closed]

In such cases the definite article is used to make a generic reference, with the result that the ‘noun phrase refers to the whole class, rather than just one or more instances of the class’(‘Longman Student Grammar of Spoken and Written English’).

We can speak about mind or the mind when speaking generally. Check out the titles of these philosophy books: they all use "Mind", not "The Mind". Then check out these science books: they use "The Mind" not just "Mind". Perhaps the difference is that the philosophy books are talking about something abstract and the science books are talking about something concrete (many scientists reject the idea of a mind-body duality and insist that the mind is actually a set of measurable brain functions) and generic, as Barrie points out. In your examples, the words are used as generics and can be replaced by your mind. In the philosophy books, mind cannot be replaced by your mind.