Thus the reason why certain intuitive minds are not mathematical is that they are quite unable to apply themselves to the principles of mathematics, but the reason why mathematicians are not intuitive is that they cannot see what is in front of them: for, being accustomed to the clearcut, obvious principles of mathematics and to draw no conclusions until they have clearly seen and handled their principles, they become lost in matters requiring intuition, whose principles cannot be handled in this way. These principles can hardly be seen; they are perceived instinctively rather than seen, and it is with endless difficulty that they can be communicated to those who do not perceive them for themselves.

Pascal, Pensées (transl. A.J. Krailsheimer)