The English translation of the Hsin-hsin Ming has various interpretations of the Chinese Character that makes up its title, most commonly as ‘Faith Heart-Mind’ or the better known ‘Trusting Mind’. And the Poem itself refers to its purpose as a ‘Life lived in True Faith’, a ‘Living in Trust’.
‘Truth’, in delightful irony is a chameleon of a word. It derives from the Old-English Treiewo, itself from the Proto–German Treuwaz. Etymological descendant of the Sanskrit Dre and Dhr [as in Dharma], it originally meant ‘Firm, Immovable’.
Around the 14th Century it began a descent in meaning to Fidelity, to a conformance’ [to the situation] and in time to simply as ‘Faith’. Truth in its deepest meaning had something to do with an ‘Unshook Trust’.
As late as the 19th Century Academic philosophers were coming up with ‘Theories of Truth’ which by that very fact vitiates its end. The Consistency Theory of Truth; the Coherence Theory of Truth; the Correspondence Theory of Truth and so on. Plato would have gulped.
If you look up modern dictionary definitions you will find explanations in keeping with the times: ‘Actuality, Certainty, Conformance with Facts, Accord with Reality’ and so on although each of these terms [‘Fact’] would itself require a lengthy elaboration.
In Martin Heidegger’s insightful take, Truth has not to do with logical propositions but rather:
‘The essence of Truth is Freedom and the essence of Freedom …is the resolutely open bearing that does not close up on itself…‘Philosophical Thinking’ is the stern and resolute openness that does not disrupt the concealing but entreats its open essence into the open regions of the understanding and thus into its own Truth.’