"Knowledge not interfused with the light of reason, not subjected to repeated tests, becomes formal and pedantic or mystical and extravagant. It loses its relation to known object matter, and ceases eventually to be knowledge at all.

Thus the first office of reason is to keep the body of knowledge healthy, by purging from it the fallacious assumptions and crude analyses which may have served in their time as steps to truth, but have become mere obstructions to those who mistake them for truths attained." - Charles E Hooper, The Anatomy of Knowledge (I think 1916 or 1917)

I really like this thinking, because it doesn't demonise religious belief as a complete waste of time. It acknowledges that it may have been a stepping stone to getting better knowledge of the world, but it also slams it as being useless now when we have better systems for attaining the truth.