Such a thinker is at the mercy of circumstances, following blindly the leadings of trains of thought which are his master instead of his servant, and which lead him anywhere or nowhere without let or hindrance from him. His consciousness moves rapidly enough and with enough force, but it is like a ship without a helm. Starting for the intellectual port _A_ by way of _a_, _b_, _c_, _d_, he is mentally shipwrecked at last on the rocks _x_, _y_, _z_, and never reaches harbor. Fortunate is he who can shut out intruding thoughts and think in a straight line. Even with mediocre ability he may accomplish more by his thinking than the brilliant thinker who is constantly having his mental train wrecked by stray thoughts which slip in on his right of way. 5. TYPES OF ATTENTION THE THREE TYPES OF ATTENTION.--Attention may be secured in three ways: (1) It is demanded by some sudden or intense sensory stimulus or insistent idea, or (2) it follows interest, or (3) it is compelled by the will. If it comes in the first way, as from a thunderclap or a flash of light, or from the persistent attempt of some unsought idea to secure entrance into the mind, it is called _involuntary_ attention. This form of attention is of so little importance, comparatively, in our mental life that we shall not discuss it further. If attention comes in the second way, following interest, it is called _nonvoluntary_ or spontaneous attention; if in the third, compelled by the will, _voluntary_ or active attention. Nonvoluntary attention has its motive in some object external to consciousness, or else follows a more or less uncontrolled current of thought which interests us; voluntary attention is controlled from within--_we_ decide what we shall attend to instead of letting interesting objects of thought determine it for us.