Sufficient employment == full employment?

This is a topic for dicussion as much as anything else. Sufficient employment to me seems a little vague and undefined. Therefore, I'd suggest full employment as the target of economic policies.

However, there's a caveat here. Is full employment necessarily possible, given the level of capacity in the economy, increased automation of manual work, etc. If it is not, do we want to acknowledge this, and instead propose something like a citizen's basic income which allows all to live in a society where under-employment is a macroeconomic fact of life?
So. Do we target full employment, through taxation ,rate-setting (and direct policies such as a job guarantee, if there' appetite for it?), or do we acknowledge that underemployment is a fact of life, and ensure that our tax system and welfare state is fit for purpose in these conditions (by ensuring that all can survive, regardless of their employment status)?