Vitality- can you guess the object?

It is thin and fragile. It can create a sketch line so pale as to be nearly invisible, or a letter as black and bold as obsidian. It can erase an idea from the visible world, or plant it in someone else’s mind. It can translate the riddles of a child’s mind into clear thoughts, or the clarity of an adult’s into a riddle. It is simple and insignificant, but in the right hands, it is vital.