XXX. Основные знаки и простейшие формулы логистики (для справок).

∙ ∶ ⫶ signs replacing parentheses (in algebra). p, q, r,... signs of judgment (sentence). a, b, c,... concept signs (classes). x, y, z,... signs of an individual. Ɔ sign of inclusion (implications for sentences and inclusion for classes). ∩ sign of logical multiplication or compatibility. ∪ sign of logical addition or alternativeness. ɜ is an operator sign that establishes the correspondence of a class to a certain sentence. ɛ sign of the operator establishing the individual’s belonging to a class (ἐστι). ι sign of a unit class. sign of an individual belonging to a unit class. ≡ numeric identity sign. Ǝ a sign of real existence. R is a binary relation sign (between two terms). ‘R is the sign of the R reversed relation. sign of relative multiplication of relations. sign of logical multiplication of relations. φx. ψx, … signs of a logical function. “If the inclusion p Ɔ q is true and if the hypothesis p is true, then the proposition q is also true, and it can be asserted separately” (VIII). (Principle of deduction). “In a general formula, you can always substitute a particular or individual term instead of a general or indefinite term” (IX). (Substitution principle). Formulas (XIV) and (XV) together define “negative”, so we can write: