a logical inference engine


this page is for entering a script of assertions and questions and having the questions automatically answered from the assertions. It doesn't think for you or understand English but it can prove that your conclusions follow from your premises and show, mercilessly, how you got from one to the other.


well, why not. There are many situations where provably sound and complete inference is a good thing: project proposals, essay plans, contract wordings, logic puzzles, general arguing with your mates down the pub.


you type your scripts in the infer input area then click the "run script" button. The infer section has some demo scripts, the refer section has the script syntax, and some articles about logic and logie.


if you sign-up with your email address you can name and save some scripts, your width, height & work areas are saved when you logout, and you get an email whenever the page changes. It's free to use but you can pay not to see the ads or to save more scripts.




start the page
logie web





logie syntax

In general logie has no knowledge about anything inside quotes, except the sequence of characters for comparison purposes. It does know about what's outside the quotes, the words like "if" and "and".




script one or more assertions or questions 'p' if 'q'. 'q'. 'p'?
assertion a factual claim or a definition of a proposition, followed by a full-stop 'p' if 'q' and 'r'.
question an expression ending in a question-mark 'p'?
factual claim a proposition or a negated proposition 'p'. not 'q'.
definition a proposition, then "if", then an expression 'p' if 'q' and 'r'
proposition a string of characters beginning and ending in quotes of the same type 'p', "q"
expression a proposition, conjunction or a disjunction or a negated expression, or another expression enclosed in ( and ); true if the various parts are true according to each type 'p' & not ('q' or 'r')
conjunction two expressions with & or and between them; true only if both are true 'p' & 'q', 'p' and 'q'
disjunction two expressions with or between them; true only if at least one is true 'p' or 'q'


  • what is logic anyway? logic and formal reasoning take a bit of explaining - have a look down this rabbit hole fr'instance.
  • so what is logie, in the grand scheme of things?
  • how to translate natural English into formal logic: there are several identifiable steps in finding the logical essence of a text.