I've been studying the Diamond Sutra in the last few days (yes, I know it's not accepted as part of Theravada), and have been relieved to find that it confirms everything I've come to believe regarding our use of concepts. In particular, in many instances the logic used takes the form of A, is not A, but named 'A'. In other words, there are no things, only the names given to things. Things only exist by virtue of their relationship to other things. There is an interdependent causal relationship, such things usually being described using the term 'conditioned', as opposed to reality free from concepts, which is termed the 'unconditioned'. When we fall back on our use of concepts, this is working within the framework of conventional (or relative) truth, whereas if we wish to approach things with the understanding that concepts are impermanent mental formations, then we are working within the framework of ultimate (or absolute) truth. So, the logic in the Diamond sutra can then be understood as "A, is not A" (conventional truth), "but named 'A'" (ultimate truth). Now, as far as compassion is concerned, I can appreciate that this falls within the framework of dualistic conventional/relative truth, and that we can apply it to our consideration regarding non-dual ultimate/absolute truth. This is valid since compassion and indeed all the other emotions could only not-be, if we were somehow able to escape from living within the framework of conventional/relative truth. This is clearly not possible, since the complete abandonment of concepts would render the world meaningless, and it would not be possible to function on any level higher than that of a new born baby. This is the reason why we are encouraged not to stifle our emotions as they occur, but rather allow them to be, whilst simply witnessing their arising and subsequent passing away without attachment. (Coupled with the knowledge that they are unsatisfactory and conceptual in nature). So, whilst not being able to abandon conventional truth, we can continue to operate from within it, with the simultaneous knowledge that from the wider perspective, reality is in the form of non-dual ultimate truth, free from concepts. Now it has also been argued that we shouldn't waste time thinking about these things, since it is just more conceptualising, and instead we should put all our time and effort into the practice of sitting. However, we know the Buddha was keen for us to exercise our powers of investigation in order to determine for ourselves what is true and what is not true, based on whether it seems reasonable. There is no such thing as blind faith in Buddhism, which as an atheist and a sceptic, is one of things which originally attracted me to it in the first place. That said, it remains vitally important to sit in order to inspire an understanding of ultimate truth at the experiential level, rather than just knowing it intellectually.
"The foolish reject what they see, not what they think. The wise reject what they think, not what they see." - Huang Po.