Choose the correct variant.

Even though chimpanzees pass the mirror test, they do not seem to conceive of others' - or even their own - mental states. I used to tell students that no one ever heard, saw, tasted or touched a mind. There is no way for me to experience your experience, ... that of a species other than my own. So although minds may exist, they fall outside the realm of science.

• let alone
• however
• not only
• considering