Philosophers, and especially analytic philosophers, often reject philosophical positions on the basis that they are nonsensical. To raise the charge of nonsense means to ascribe to someone a failure that is much more fundamental than mere falsehood, for to utter nonsense means to have failed to express a thought, i.e., that which could be said to be either true or false. Nonsensical expressions fall short of some necessary condition that must be met if an expression is to have content at all. It has therefore been a central concern of analytic philosophers to develop a theory of meaning that allows one to distinguish between meaningful and nonsensical expressions. The concept of nonsense is therefore central to philosophical semantics.
Whilst a theory of meaning could account for what characterizes nonsensical expressions as such consists in, it cannot account for the possibility of engaging in nonsense. Nonsense is a kind of an epistemic predicament. For the concept of nonsense entails that it appears to one that an expression is meaningful, whereas in fact it is in fact a mere string of symbols or vibrations through the air. The question of how such an illusion of sense even arises must further be investigated from the vantage point of epistemology.
If one relies on this characterization of nonsense alone, one may conceive of nonsense as a kind of ailment plaguing rational discourse that philosophy seeks to diagnose and alleviate from within the bounds of sense. This picture of philosophy’s relation of nonsense is in fact naïve. For one, philosophical investigations often consist in setting up and thinking through a certain conception, only to recognize it as nonsensical and thereby arrive at philosophical insight. How can we reason through that which is completely unintelligible, i.e., doesn’t express any determinate thought? A philosophical position is in this case dealt with not by advancing an argument in the strict sense of the word but by means of a philosophical elucidation, i.e., a deliberate construction of nonsensical strings of words of a particularly misleading character, so as to allow the one who recognizes them to be in fact void to gain a certain kind of philosophical insight.
The previous point has not only cast some doubt on the naive picture of the relation of philosophy to nonsense, but has put another, somewhat disquieting conception into view of nonsense playing a role in apagogical philosophical argumentation. The disquiet mounts when we consider the status of ostensive philosophical arguments and thereby of philosophical theories themselves. If a philosophical theory specifies the conditions that expressions need to fulfill in order to be meaningful and thereby draws up the bounds of sense, the expressions that the theory is formulated in must lie beyond these bounds. The investigation of the concept of nonsense thereby raises the meta-philosophical question of whether philosophy itself is nonsense.