logical truth
The idea that there is some special collection of truths which should be called logical truths, among which number those truths which can be logically proven is widespread.
There are however substantive disagreements about what these truths are, for example, about whether they include the truths of arithemetic.
Furthermore, I know of no account of logical truth which encompasses all the truths which are obtainable within any proposed logical system.
For example the results of inductive inference (meaning here scientific rather than mathematical induction) are not generally held to be logical truths.


deductive or demonstrative
It is therefore only reasonable to expect the idea of logical truth to encompass a subset of the logics which have been formulated.
A first indication of the kinds of logic which we might expect to be encompassed by a definition of logical truth is deductive or demonstrative logic, the primary feature of which logics is that we have generally reasonable grounds for believing that they are sound in the sense that only true conclusions are derivable from true premises.


defining logic
Quine has defined logic (in [Quine70]) as "the systematic study of the logical truths".
Our own preferred definition is that logic "is the study of necessary truths and of systematic ways of expressing and establishing such truths".
Clearly either one of these does not take use very far and the proof of the pudding is not to be had until considerable further elaboration has been supplied.


