The E Theorem Prover


E is a theorem prover for full first-order logic with equality. It accepts a problem specification, typically consisting of a number of first-order clauses or formulas, and a conjecture, again either in clausal or full first-order form. The system will then try to find a formal proof for the conjecture, assuming the axioms.

If a proof is found, the system can provide a detailed list of proof steps that can be individually verified. If the conjecture is existential (i.e. it’s of the form “there exists an X with property P”), the latest versions can also provide possible answers (values for X).

Development of E started as part of the E-SETHEO project at TUM. The first public release was in in 1998, and the system has been continuously improved ever since. I believe that E now is one of the most powerful and friendly reasoning systems for first-order logic. The prover has successfully participated in many competitions.


E 2.4 Sandakphu is now available. This version is a cleaned-up release of the CASC-27 version. The main changes over E 2.3 are support for additional calculus variants, better search heuristics, and much improved automatic modes.

The new version is available from the Download page.

E 2.4 Sandakphu (pre-release) has won the UEQ division of CASC-27 in Natal, Brasil. It has also won second places in FOF and LTB, and was an important component of Satallax (winner of TFH) and LEO-III (winner of LTB). We will try to release a polished version in the next days. Until then, it is available via the public github repository.

Latest news