The plays of Ionesco, along with the work of Samuel Beckett, Jean Genet, and Arthur Adamov, became the foundation for the theatrical movement known as the Theater of the Absurd. This movement was defined by Martin Esslin in his important book entitled (you guessed it) The Theater of the Absurd.
On the whole, these writers seemed to be inspired by the philosophy of Existentialism, popularized by Jean-Paul Sartre, and the idea of the Absurd as articulated by Albert Camus. Basically, they believed that there is no great purpose in life, therefore everything we do is meaningless or absurd. Ionesco said that, "Absurd is that which is devoid of purpose…Cut off from his religious, metaphysical, and transcendental roots, man is lost; all his actions become senseless, absurd, useless" (source). In the minds of the Absurdists, it was each individual's responsibility to create meaning for himself. This philosophy can be seen throughout The Chairs.
The Old Man bears all the hallmarks of a typical Absurdist hero.
The Old Man's message goes against the ideas of Existentialism because it proposes the existence of an absolute, objective truth.