Aristotelian causal theories incorporate some philosophically important features of the concept of cause, including necessity and essential character. The proposed formalisation is restricted to one-place predicates and a finite domain of attributes (without individuals). Semantics is based on a labelled tree structure, with truth defined by means of tree paths. A relatively simple causal prefixing mechanism is defined, by means of which causes of propositions and reasoning with causes are made explicit. The distinction of causal and factual explanation are elaborated, and examples of cyclic and convergent causation are given. Soundness and completeness proofs are sketched.