LibriVox

LibriVox volunteers record chapters of books in the public domain, and then we release the audio files back onto the net for free. All our audio is in the public domain, so you may use it for whatever purpose you wish.

We get most of our texts from Project Gutenberg, and the Internet Archive hosts our audio files (for free!).

https://librivox.org/

In the catalogue check out Non-Fiction > History and Non-fiction > Philosophy in the Genre/Subject index.