Introverted Sensing (Si) is one of the 8 information elements in Socionics — introverted, sensing, irrational and perceptive. Si is the Leading function for SEI (The Mediator) and SLI (The Craftsman), and the Creative function for ESE (The Enthusiast) and LSE (The Director).
An irrational, perceptive attitude oriented toward the inner world. Si perceives the stability, sanity and established order of experience — noticing deviations from what is known, trusted and proven.
Definitions
Introverted — primarily concerned with one's own thoughts, feelings and internal states; oriented inward rather than outward.
Sensing — sound practical intelligence; sanity; a realistic point of view; direct, grounded perception of what is.
Together, Si is the capacity to perceive the world in terms of what is established, stable and proven — and to notice whenever reality deviates from that norm.
In Practice
"The map is not the territory" — except for Si, the map essentially is the territory. Established order is not an approximation of reality; it is reality. Change for its own sake introduces chaos that cannot coexist with the stability Si demands.
"Tried and tested" — the methodology of Si: keep things stable by using techniques proven to work, and treat them as society's default expectations. The 9-to-5 work ethic has existed for decades — why change it?
"Sometimes a cigar is just a cigar" — £5,000 in the bank is £5,000 in the bank, as printed on the balance statement. Si implies no further facts; it takes experience at face value without extrapolating into possibility.
"If you do what you have always done, you will get what you have always got" — Si's operating principle. Consistency is sanity; deviation is risk.
Si is the direct opposite of Ne. Where Ne perceives everything as pointing toward something else, Si perceives things as being precisely what they are. It naturally labels original or unexpected behaviour as irregular, and works to maintain the subjective norms it has built from accumulated experience. Once Si has decided something is sound, it holds that judgement until a trusted source provides compelling reason to revise it.
Model A Positions
Si appears at a different position in every type's Model A, which determines how consciously and actively it operates.
Noticing discrepancies in the social realm; observing the external world carefully; forming conclusions about personal mindsets and whether they reflect lived experience; opinions and behaviour toward others based on established preconceptions.
Cautiously acquiring data about the external world; tentatively constructing explanations for apparently chaotic situations; building an internal reference guide for coping with observable irrationalities.
Forming opinions based on subjective experience but reluctantly; avoiding dealing with apparently chaotic situations; stabilising reality not viewed as a priority; the sustained effort of creating order out of chaos quickly exhausts and provokes them.
Subtle curiosity toward apparent chaos in the environment; attracted to the unknown in an attempt to rationalise it; drawn toward situations with an element of chaos and adventure; a deep-rooted desire for someone who can make sense of sensory reality on their behalf.
Speculating the reality of situations lacking in empirical evidence; quietly expecting others to fill the gaps in their grounded tactile intelligence; a deep-rooted desire for a healthier, more ordered lifestyle; subdued reactions to perceived chaos or threat.
Collecting information about perceived chaos in the external world, held dormant; storing opinions and behaviours based on immediate observations; maintaining a growing data-bank of subjective experience; an "innocent until proven guilty" default perception.