Friar Lawrence finds himself in a very difficult position in Act IV scene 1. It is essential to understand how dramatic irony works in this scene, as Friar Lawrence and the audience know what Paris is blissfully unaware of: that Juliet is already married and her grief for her cousin Tybalt is also a result of the banishment of her husband. Therefore Friar Lawrence cannot reveal this truth to Paris, and he can do nothing accept express his concern at the speed of the marriage that is being proposed. Note how he expresses this concern and does what he can to try and encourage Paris to slow the process so he can have more time to bring about Romeo's return:
You say you do not know the lady’s mind.Uneven is the course. I like it not.