"Essentialism", an emphasis on 'essences' expressed in definitions and a rigid insistence on 'laws of thought' characterize what Korzybski called the aristotelian orientation. But despite the essentialism which Aristotle got from his teacher Plato, Aristotle himself went beyond it in several ways that show he was not himself a strict 'aristotelian'.
For example, although Aristotle systematized the search for essences in his logical works, the focus of this search for him seems somewhat different from that of Plato.
Plato had clearly emphasized the secondary importance of the visible world compared to the more important world of ideal forms or essences that he postulated. Aristotle, on the other hand, emphasized the importance of the world we live in, with the forms or essences existing within the objects around us that we see and touch.
Despite the essentialistic drift of his logic, this 'realistic' bent of Aristotle makes his philosophy in some ways more congenial with Korzybski's "non-aristotelian" perspective than some people might expect. There are places in his writings related to logic and methodology where Aristotle indicates some quite non-aristotelian sounding (in the korzybskian sense) leeway in what are still referred to as the aristotelian "laws of thought".
For example, in Metaphysics, he wrote: "...however much all things may be 'so and so', still there is a more and a less in the nature of things." (Book IV: Ch. 4, p. 743) In De Interpretatione, he noted that certain statements may have an "undecided" or indeterminate value, neither "true" nor "false". For example, take the statements "A sea-fight will take place tomorrow."
"One may indeed be more likely to be true than the other, but it cannot be either actually true or actually false. It is therefore plain that it is not necessary that of an affirmation and a denial one should be true and the other false." (Ch. 9, p. 48)
Aristotle also moved beyond the two-valued approach of his logic in his work on ethics and politics. In Nichomachean Ethics, he emphasized the doctrine of the "golden mean", which involves each individual finding the best intermediate third value between two extremes. So courage provides a mean between excessive fear and over-confidence, and temperance lies between the extremes of self-indulgence and 'insensibilty'. (Book II: Ch.7, pp. 959-960)
In his Politics, he emphasized that the individual and society did not have to exist in opposition to each other: "Man is a political animal" who develops his excellence in the company of others, while the State can function to aid the individual in his self-development.
Despite these exceptions, Aristotle and followers put into place a system that, when carried into the orientation of everyday evaluating and science, became rigidified. This "aristotelian" orientation has outlived its usefulness as an overarching approach.
Korzybski emphasized his admiration for Aristotle even as he criticized and sought to go beyond aristotelianism:
"To avoid misunderstanding I wish to acknowledge explicitly my profound admiration for the extraordinary genius of Aristotle, particularly in consideration of the period in which he lived. Nevertheless, the twisting of his system and the imposed immobility of this twisted system, as enforced for nearly two thousand years by the controlling groups, often under threats of torture and death, have led and can only lead to more disasters. From what we know about Aristotle, there is little doubt that, if alive, he would not tolerate such twistings and artificial immobility of the system usually ascribed to him." (Science and Sanity, Fifth Edition, p. xciv)
To conclude, Korzybski was certainly NOT anti-Aristotle nor anti-aristotelian logic. Instead, he objected to aristotelianism as an orientation or system involving the basic structural assumptions about the world ('metaphysics') and human knowledge ('epistemology') that he saw underlying Aristotle's systematic views (epitomized in the view of aristotelian logic as 'the' logic). Korzybski felt the need to challenge and revise these structural assumptions in the light of later scientific investigations, since overemphasizing aristotelian logic as 'the' logic encouraged an essentialist, what he called an "intensional" orientation in science and life, involving "identification" or "confusion of orders of abstraction". For Korzybski, aristotelian logic still had a place in useful formulating but could no longer be given an exclusive or dominating position. The main emphasis of Korzybski's work in "general semantics" (GS) was not on 'logic' as such, but on what might be called "psycho-logic", i.e., understanding and enhancing the entire scope of human evaluating including thinking-feeling-perceiving-doing, etc.; our evaluational reactions.
McKeon, Richard. 1941. The Basic Works of Aristotle. New York: Random House.