""Faith" is a fine invention" by Emily Dickinson's main idea is "faith" is real for people who see faith through the naked eye, but for those who don't they rely on science to figure things out for them. So also in the poem it says that in the end or " in and emergency" science will win over faith.
In the poem it puts quotation marks around the word "faith" as if she was being sarcastic talking about religion, so she obviously didn't really believe in faith. In the second line it says " for gentlemen who see" and in that line its saying that for people who believe in faith, good or you, but if you don't believe in faith good for you. In the third line it says, " by microscopes are prudent" in this line its mainly referring to science in saying that it is the wiser choice over faith. And in the final line when it says, " in an emergency" it means, in the end science over faith will get you farther in a bad situation.