Since, however, even though we might not be able to undertake any thing in relation to an object,c and taking something to be true is there fore merely theoretical, in many cases we can still conceive and imagine an undertaking for which we would suppose ourselves to have sufficient grounds if there were a means for arriving at certainty about the mat ter; thus there is in merely theoretical judgments an analogue of practical judgments, where taking them to be true is aptly described by the word belief, and which we can call doctrinal beliefs.d If it were possi ble to settle by any sort of experience whether there are inhabitants of at least some of the planets that we see, I might well bet everything that I have on it.