Is there wisdom which actually cannot be fully expressed except in poetry or
As Nicholas suggests, it partly depends upon what you mean by 'wisdom'. Many philosophers (and others) have been attracted to the idea thatart provides a kind of experientially-based 'insight' that pureargumentation cannot supply. One possibility here is that there are properties or propositions that we (or at least, most ordinary people living fairly ordinary lives) can only become acquainted with through art. This might be because the art provides a kind of substitute experience for a reality most of us will never experience (e.g. slogging through the fog of war), or because the art provides an experience that simply does not occur in real life (e.g. the sublimity of a symphony). Another possibility is that art provides us with a perspective on, or a mode of presentation of, properties or propositions that we might already be independently acquainted with; but that this perspective or mode of presentation leads us to appreciate the familiar propositions in a more profound and intimate way. Thus, Crime and Punishment might lead us to appreciate the truth of the cliche that "crime doesn't pay." Finally -- what to me seems intuitively closest to the notion of wisdom -- some people think that engaging with art can train our cognitive and emotional faculties to respond to real life in a more mature, nuanced manner. Thus, Martha Nussbaum (cf. esp. Love's Knowledge) suggests that novels are uniquely equipped to help us appreciate and negotiate the complex, highly context-laden challenges of ethical action because they provide us with a rich, experiential engagement with complex and ethically challenging characters and situations, in a context where our perceptions are not clouded by self-interest as they typically are in actual life, and where the author actively helps us to see things in an ethically responsible way.