We start then from the natural isolation and severance of minds. Their experiences at the best, under the most favourable circumstances, can be but similar. Communication, we shall say, takes place when one mind so acts upon its environment that another mind is influenced, and in that other mind an experience occurs which is like the experience in the first mind, and is caused in part by that experience. Communication is evidently a complicated affair, and capable of degrees at least in two respects. The two experiences may be more or less similar, and the second may be more or less dependent upon the first. If A and B are walking in the street together and A touches B and says, “There is the Lord Chief Justice,” B’s experience while he contemplates the dignitary is only adventitiously dependent upon A’s experience. But if A, having met the Lord Chief Justice, describes him to a friend afterwards in a quarry at Portland, for example, his friend’s experience will depend very largely upon the particular judges he may himself have encountered, and for the rest will derive its special features from A’s description. Unless A has remarkable gifts of description and B extraordinarily sensitive and discriminating receptive ability, their two experiences will tally at best but roughly. They may completely fail to tally without either being clearly aware of the fact. In general, long and varied acquaintanceship, close familiarity, lives whose circumstances have often corresponded, in short an exceptional fund of common experience is needed, if people, in the absence of special communicative gifts, active and receptive, are to communicate, and even with these gifts the success of the communication in difficult cases depends upon the extent to which past similarities in experience can be made use of. Without such similarities communication is impossible. Difficult cases are those in which the speaker must himself supply and control a large part of the causes of the listener’s experience; in which correspondingly the listener has to struggle against the intrusions of elements from his own past experience which are irrelevant. When A can point and B gaze, the matter is sometimes easy; although, as is well known, a complex object, for example a landscape, where many different selections are possible corresponding to different emphases of interest, cannot be dealt with in so simple a manner. Less complex things in which the interesting feature is more salient, for example, a gentleman asleep in Church, may be merely indicated with more confidence of communication, although here again one person may feel indignation and another amusement at the sight.