If you will, join me for a discussion on what it means for different types to perceive the same ball.

An INTP and an INTJ come upon a ball. The ball is completely still. Although both the INTP and the INTJ recognize the ball exists, they use different functions to perceive it.

The INTP perceives that the ball is exterior to himself. He does this by witnessing it with his eyesight. He is reacts to the fact that the ball is not moving by determining that it is, indeed, not moving.

The INTP uses each of his unconscious functions in the act of perceiving the existence of the ball:
- The ball is external to himself (extroversion)
- The ball is perceived through the use of his senses (sensation)
- He reacts to the presence of the ball (feeling)
- He observes that the ball is not moving (judgement)

From the perspective of the INTP, the ball is an unconscious personality, because he uses his unconscious functions to perceive it. Indeed, it has qualities that correspond to each of his unconscious perceptions of reality: tangebility, material, state.

The INTJ observes the ball also. He notices that it is not a part of his own identity, and is therefore a part of the external world. He comes to this conclusion by witnessing the ball with his external vision. He reacts to the presence of the ball by perceiving that it is not interacting with the world around it, and is in a state of rest.

Like the INTP, the INTJ attributes his unconscious functions to the ball:
- He internally processes that the ball is external to himself. (extroversion)
- He senses that the ball is visible (sensation)
- He observes that the ball will react if it is touched (feeling)
- He notes that the ball is at rest (perception)

Like the INTP, the INTJ perceives the ball as an aspect of his unconscious personality.

Two points worth noting:
- The INTP and the INTJ observe the ball as having different irrational functions (to the INTJ, the ball has a perceptive quality because it is capable of movement; to the INTP, the ball has a character of judgement because it is not in motion)
- The INTP and the INTJ observe that they observe the same ball. They observe that their conclusions, therefore, must be symmetrical to each other, even their differening conclusions about its irrational character. They imply, therefore, that for both to observe the same reality, there must be a way to reconcile their differences in perception.