A fool who is pleased might stop doing harm and start doing useful work. In this sense it is wise to praise a fool; it helps to motivate him. So your praise is meaningful when it is directed towards a fool. A wise man by his nature will continue doing good work because his attitude does not depend on someone’s praise or blame. So it serves no purpose to praise a wise man because your praise will have no impact on him.
There are three types of people – the wise, the crooked and the immature.
The wise man continues doing good work whether he is scolded or praised.
Crooked people need to be praised to get them to do good work.
And from time to time immature people need to be both praised and scolded for them to do something good.