Glossary: Irrational Functions

The axis which contains the intuition and sensation functions. Not dependent on reason (whether abstract thinking or judgment). Things perceived by the irrational functions aren’t considered irrational because they are illogical, but because they don’t require logic, they simply are. Facts are examples of things that are irrational. (See also “rational functions.”)

Intuitive individuals talk about ideas and have no difficulties with allusions or reading between the lines, while Observant types focus on facts and practical matters. This is why Intuitive types are likely to find it quite challenging to understand someone with the Observant trait, and vice versa. The former may even think that the latter is materialistic, unimaginative and simplistic, and the latter may see their Intuitive conversation partner as impractical, naïve and absent-minded. Both sets of assumptions can be quite damaging and it takes a mature person to get past them – but statements like these are fairly common.

- "The 5 Aspects" (16 Personalities)

Both intuition and sensation are functions that find fulfilment in the absolute perception of the flux of events. Hence, by their very nature, they will react to every possible occurrence and be attuned to the absolutely contingent, and must therefore lack all rational direction. For this reason I call them irrational functions, as opposed to thinking and feeling, which find fulfilment only when they are in complete harmony with the laws of reason.

“Definitions,” pars. 776f

Jung pointed out that elementary existential facts fall into this category - for instance, that the earth has a moon, that chlorine is an element or that water freezes at a certain temperature and reaches its greatest density at four degrees centigrade - as does chance. They are irrational not because they are illogical, but because they are beyond reason.

Sharp, Daryl, “Jung Lexicon”