Quicquid corporis nostri agendi potentiam auget vel minuit, juvat vel coercet, ejusdem rei ideamentis nostræ cogitandi potentiam auget vel minuit, juvat vel coercet.
English (Elwes 1883)
Whatsoever increases or diminishes, helps or hinders the power of activity in our body, the idea thereof increases or diminishes, helps or hinders the power of thought in our mind.
Modern English
Whatever increases or diminishes, helps or hinders the power of activity in our body — the idea of that thing increases or diminishes, helps or hinders the power of thought in our mind.