Bakhtin's thought can be characterized as "unsystematic" for two reasons.
First, Bakhtin's work spanned categories. He made major contributions to philosophy, linguistics, semiotics, and literary theory, which makes categorizing or attaching him to one particular school of thought (e.g. structuralism, post-structuralist, materialism, etc.) very difficult. But he also disdained systematic theories, especially of language. He argued that language (and culture) is inherently social, not created by rules but developing organically through dialogue. The contention seems to be not that Bakhtin was a scattered or diffuse thinker, but that his work generally rejected overly rigid systems and structures as intellectual constructs. As on Bakhtin scholar observes, one of Bakhtin's defining characteristics was his “relentlessly speculative approach to language, literature, and the human universe.”