Sentence:  In matters of the intellect do not pretend that conclusions are certain which are not demonstrated or demonstrable. That I take to be the <WSD>agnostic</WSD> faith, which if a man keep whole and undefiled, he shall not be ashamed to look the universe in the face, whatever the future may have in store for him. 
Meaning of the word marked with <WSD> tags:  Of or relating to agnosticism or its adherents.