"With it we bless our Lord and Father, and with it we curse men, who have been made in the likeness of God; from the same mouth come both blessing and cursing. My brethren, these things ought not to be this way. Does a fountain send out from the same opening both fresh and bitter water? Can a fig tree, my brethren, produce olives, or a vine produce figs? Nor can salt water produce fresh." (James 3:9-12)Duplicity is being doubly contradictory in our lives. We think, say, and do one thing in one context and we thing, say, and do something completely different in another. We bless God in church on Sunday, yet at work on Monday we gossip, backbite, and revile those coworkers and associates we don't like as much. We have become like that double-minded man that James spoke of who was always shifting, changing, and "unstable in all his ways." (James 1:8)
One of the problems with being duplicitous is that people see right through us. We think we are being sophisticated and coy, but other people know the real score. People see through our disguises to our real self. They see our duplicity and tune us out. It is like when Lot went to warn his sons-in-law about the coming destruction of Sodom and Gomorrah. "Lot went out and spoke to his sons-in-law, who were to marry his daughters, and said, 'Up, get out of this place, for the Lord will destroy the city.' But he appeared to his sons-in-law to be jesting." (Genesis 19:14) Why did they take him for jesting? Because this was the kind of man he was. They probably saw him jesting before, even in the context of God and morality. He never seemed to care much for it before so why should they listen to him now?
I've seen this happen in families. On Sunday the parents speak wonderfully about God and their love for Him, but the rest of the week they are mean, harsh, and biting in their words. This leaves the children confused and they are often not likely to take seriously the message of the gospel which is so quickly replaced in the lips of their parents by harsh words. This is true not only of parents but of all who are duplicitous in their speech and behavior. Our speech must be consistent if people are to take us seriously and to give full consideration to the gospel we proclaim with our lips and with our lives. Jesus said, "Either make the tree good and its fruit good, or make the tree bad and its fruit bad; for the tree is known by its fruit." (Matthew 12:33) So should be our lives. Either we should be consistently good or consistently bad for duplicity does no one any good.
Finally, when we speak one way of God and another way of man, it reveals an ignorance in our learning of God. God created all things and, especially of mankind, "God created man in His own image, in the image of God He created him; male and female He created them." (Genesis 1:27) If we love God should we not also love His creation and especially those created in His image? It is said of God's creation, "God saw all that He had made, and behold, it was very good." (Genesis 1:31) Should we not love that which is very good? Should we curse what God has blessed? We are often used to looking up at God through our own eyes but perhaps we should learn to look down at creation through His eyes. If we really learned to see this creation as He sees it, them maybe we would not be so quick to curse what He Himself has made.