Why did Timothy try to help Phillip after he discovered he was blind?

In the book The Cay Timothy is a kind older black man ho is from the Caribbean Islands.  He has been treated rudely by Phillip on the raft after they had been torpedoed and their ship destroyed.  However, he knows that Phillip is only a boy and can not take care of himself.

Because they are the only two that appear to have survived the ship's destruction with a cat, named Stew Cat, he must be the one to help the lad.  He recognizes that if he does not teach the boy how to survive and fend for himself despite his blindness that if something happens to him, the boy would die.