We have laid down the general principle that obstruction of mental activity is painful, and its furtherance pleasant. This is true, if properly understood; but there are complications which are apt to cause confusion if they are not carefully explained. Above all, it must be noted that an obstacle to the attainment of an end does not necessarily bring mental activity to a standstill. What is really painful is dead strain comparable to pushing against an unyielding wall. But an obstacle, whether formal or material, to the attainment of an end, may heighten instead of arresting, the flow of ideas, just as the dangers of mountaineering call into play the resources of the climber, thereby increasing his bodily and mental activity, and contributing to his pleasure. A difficulty in face of which a man feels himself helpless, is painful in proportion to the strength of the cognitive tendency which it thwarts. On the other hand, a difficulty which calls his powers into fuller and more varied play, may be a source of pleasure. Whether it will be actually so or not, depends upon the special conditions of the case. It is necessary to distinguish between two kinds of end: in the one, it is part and parcel of the end that it should be attained in a certain way by our own activity; in the other, it is a matter of indifference whether it occurs with or without our cooperation. If we are trying to hit a mark with a stone, it will give us no satisfaction for somebody else to hit the mark; it will give us no satisfaction to walk up to the mark and place the stone on it. So in guessing a riddle it gives us comparatively little satisfaction to be told the solution; the pleasure lies in finding it out for ourselves. On the other hand, if we are hungry and desire food, we are perfectly content to have it placed on the table for us. Our satisfaction is not at all diminished by the fact that we did not prepare it ourselves; on the contrary, the necessity of preparing it ourselves would in most cases be an actual drawback. We have stated the contrast between these two kinds of ends, so as to bring out the antithesis between them as sharply as possible. But as a matter of fact, they are for the most part blended with each other, satisfaction lying partly in the attainment of the final result, which we may call the material end, and partly in the process of attaining it, which we may call the formal end. We may suppose that CEdipus was a man who delighted in guessing riddles; and ordinarily his satisfaction would lie in finding out the answer for himself. But when he had to deal with the Sphinx, his satisfaction would mainly consist in the deliverance of Thebes and in his own escape from being eaten. Now in the case of an ordinary riddle, difficulty would be mainly a source of pleasure, — because it would give scope for the fuller exercise of his mental powers. But in guessing the riddle of the Sphinx, the conditions are essentially altered; for here the welfare of Thebes and his own life were at stake, and these interests had a much greater relative importance than the exercise of his ingenuity in guessing riddles. Thus inasmuch as the difficulty threw doubt on the attainment of the material end, it would bring unmixed pain, which would probably overwhelm and overbear the ordinary pleasure of CEdipus in overcoming intellectual obstacles.

We may sum up as follows. The continuance of a conation in face of an obstacle gives rise to mere dead strain, and is therefore painful, in so far as the subject feels himself powerless to deal with the obstacle. On the other hand, so far as the obstacle calls into play the resources of the subject to overcome it, it heightens free mental activity, and to that extent gives rise to pleasure. But even in this case a condition of pain is introduced if and so far as the presence of the obstacle makes doubtful the attainment of that final result of activity which we have called the material end. The pain is the greater, the stronger the doubt is, and the greater the importance of the material end.

We must carefully distinguish between obstructed activity and diminished activity. An obstacle blocking the onward progress of a train of thought has for its first effect an intensification of the cognitive tendency which it renders ineffective. It is only in a gradual way that the conation diminishes in intensity, until it is displaced by some other activity. This takes a longer time the stronger the interest involved.

The removal of an obstacle, either by our own activity or by external circumstances, is a source of pleasure. The resulting pleasure is by no means a mere equivalent of the pain of previous obstruction. Sometimes it is less, and very often it is greater. When the preceding tension is not too prolonged and intense, the pleasure of relief for the most part exceeds the pain which is its precondition. Thus such an activity as solving a chessproblem is predominantly pleasing, in spite of periods of dead strain, in which there appears no hope of solution. So a novel with a good plot creates pleasure by a series of alternating checks and releases of mental activity. The extreme case is found in certain forms of the ludicrous. A pun impels the mind to identify objects utterly disconnected with each other. This of course involves a conflict, and an obstruction of the flow of thought. But the obstruction is so transient that it scarcely gives rise to anything that can be called pain at all. On the other hand the relief which comes with insight into the true state of the case may be a source of keen pleasure. Mental activity suddenly obstructed and so heightened is immediately set free, and is so much greater than the situation demands that it has nothing to do but enjoy itself.

It should be noted that the same conditions which increase or further mental activity may also be the conditions which initially excite it. Let us take the case of a man who finds, either that he has come into a fortune, or that he has lost one. Consider first the sudden transition from poverty to riches. One effect may be the opening of the field for the satisfaction of cognitive tendencies which actually played a large part in his conscious life in the period of poverty. But besides this there will be many tendencies which were comparatively latent while he remained poor, partly because they were displaced by more pressing needs and partly because of the hopelessness of attempting to satisfy them. The sudden accession of wealth will open a free field for the satisfaction of these previously latent tendencies, and it will at the same time transform them into conscious conations. In the opposite case of the rich man becoming poor, many conscious ambitions and projects will be crushed; but besides this there is much in his mode of life as a rich man to which he has paid no attention because it has been a mere matter of course and of routine. But his routine habits, so soon as they are obstructed by poverty, become changed into conscious conations; the same condition which denies these conations satisfaction, calls them into being.