He says that he wanted to seal his lips. But the fire burned within and he spoke. Have you determined that you would keep silent and would not flare up or give way to rage . . . No one can tame the tongue. James's point is that no man can tame the tongue.
Men can tame every animal but no man can tame the tongue.
However, there is the suggestion here that there may be help from another source. My brethren, these things ought not to be this way. Neither can salt water produce fresh. The illustrations that James uses give us the clue. If you saw a fountain that produced brackish water one minute and fresh water the next it ought to occur to you that there are two sources of supply.