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Jung’s Si, Abridged - Psychological Types
This type is oriented by the intensity of his subjective perceptions, rather than the intensity of external stimuli. As a result, it’s impossible for an outsider to reliably predict what will excite or make an impression on him. His introverted attitude stands between himself and objective reality, and in extreme cases, it’s almost as if he were shielding himself from the latter’s influence. He keeps his physical environment in a state of comfortable homeostasis for this reason. The too high is damped down, and the too low raised up, to match his subjective formula. If he’s blindsided by a particularly strong sensation, or his environment is disrupted, his oddly disproportionate reaction will demonstrate his unrelatedness to objective reality.
He might stand out by his calmness and rational self-control in the face of turbulent conditions, but it has nothing to do with rationality. He devalues the objective influences, his subjective perception standing over and above them, and this being the decisive factor in his actions and decisions. If he had a way of expressing himself, for example if he were a creative artist, the irrational and idiosyncratic nature of his perceptions would be apparent. His articulate judging functions are relatively unconscious, so they aren’t much use. Therefore, this type is one of the most difficult to understand, both for himself and for others.