This impressive bust of Aristotle is a Roman copy of a bronze original by Greek sculptor Lysippos, who lived in the fourth century BCE.

c. 350 BCE

ARISTOTLE’S ORGANON

The Greek philosopher Aristotle (384–322 BCE) touched upon several influential topics during his life that are still of interest to AI researchers today. In his book Politics, Aristotle speculated that automatons could someday replace human slaves: “There is only one condition in which we can imagine managers not needing subordinates, and masters not needing slaves. This condition would be that each instrument could do its own work, at the word of command or by intelligent anticipation, like the statues of Daedalus or the tripods made by Hephaestus, of which Homer relates that ‘of their own motion they entered the conclave of Gods on Olympus,’ as if a shuttle should weave of itself, and a plectrum should do its own harp playing.”

Aristotle also pioneered the systematic study of logic. In his Organon (Instrument) writings, he provides approaches for how to investigate truth and how to make sense of the world. The primary tool in Aristotle’s toolkit is the syllogism, a three-step argument such as, “All women are mortal; Cleopatra is a woman; therefore Cleopatra is mortal.” If the two premises are true, we know that the conclusion must be true. Aristotle also makes a distinction between particulars and universals (i.e., general categories). Cleopatra is a particular term, whereas woman and mortal are universal terms. When universals are used, they are preceded by the words all, some, or no. Aristotle analyzed many possible kinds of syllogisms and showed which of them are valid.

Aristotle extended his analysis to syllogisms that involved modal logic—that is, statements containing the words possibly or necessarily. Modern mathematical logic can depart from Aristotle’s methodologies or extend his work into other kinds of sentence structures, including ones that express more complex relationships and ones that involve more than one quantifier, as illustrated by this sentence: “No men like all men who dislike some men.” Nevertheless, Aristotle’s deep study of logic is considered to be one of humankind’s greatest achievements, providing an early impetus for many developments in mathematics and AI.