Strange, isn't it? Maybe the key is to appreciate that not all "containment" or things with an inside are physical or spatial. So we might talk about how a theory of justice should contain or include an account of property rights or a theory of what the mind is should contain an account of the origin of mind. And we might talk about what is inside or included in a concept or theory we might even speak of trying to get inside someone else's mind --which (I hope) is not a literal matter but a metaphorical way of speaking about understanding someone else's thoughts and feelings! Pointing out that we use the language of "containment" and "Inside" in nonphysical, non-spatial contexts may make things seem more mysterious than ever! But perhaps we need to appreciate that our language and ways of thinking about ourselves invovles more than speaking of concrete spatial things that contain things, like the way our brain is contained in our head!
Read another response by Charles Taliaferro
Somethings are said to exist in the mind rather than in the real world but can something really be said to exist "inside" the mind? Doesn't that assume that the mind can contain things?