The body needs careful culture, that it may be kept in a healthy condition. So the mind needs to be strictly disciplined, lest it shall be unduly developed in some things and insufficiently developed in others. Because these susceptible organs are not in your sight, where you can see the harm that you are doing to your intellectual powers and how much they need regulating, you are not conscious of the harm you are doing them. You entertain unsound theories, and your mind is made to serve these theories. (2MCP 376.3) MC VC