There are some places where chivalry is still practiced but it seems to be dying. The same could be said about good ole fashion manners. My observation over the last handful of years is common sense is declining at an alarming rate too. 

James 4:17 is the last verse of that chapter. In this verse, James appeals to people's common sense of life, but uses the entire chapter leading up to that appeal to provide a list of good things they ought to do. 

James 4:17 says, "If anyone, then, knows the good they ought to do and doesn’t do it, it is sin for them." Prior to this statement, James mentioned concerns that needed addressing in our relationship with each other and our relationship with God. Fights, quarrels, covetousness and even murder come from not placing God first in your life and asking Him about things with the right motive. (verses 1-5)

Next, we are told to sever or totally cut away the world and all of it's systems/trappings. We do this by humbling ourselves before God and relying on His provision in our lives. (verses 4-6) Jesus speaks to this in Matthew when He said,  “No one can serve two masters. Either you will hate the one and love the other, or you will be devoted to the one and despise the other. You cannot serve both God and money." (Matthew 6:24)

On the heels of this instruction James lists some nuggets of truth to hold onto, mainly referring to our relationship with God. "Submit...", "Resist...", "Come near...", "Wash and purify...", and "Humble yourselves...". (verses 7-10) Then James returns to the treatment of one another. He says, "Brothers and sisters, do not slander one another." (v.11)

One more bit of advice James gives us - we are not personally guaranteed tomorrow, as such we should recognize who grants us every breath and say, "If it is the Lord's will we will live and do this or that." (verses 13-16)

James then says, in a manner of speaking - So, now that you have a good starting point for what you ought to do, do it because not doing it is an affront to God. Add these things to your common sense and Do The Right Thing.

"If anyone, then, knows the good they ought to do and doesn’t do it, it is sin for them."