Almost universally understood to mean that the detail is getting in the way of seeing the bigger picture. You cannot see the shape of the woodland, only trunks, leaves, branches & bark.
Few stop to think that it can also go the other way.
Trees are made of wood – or at least that is what you get when you chop them down (or chop bits off) & leave them to season.
An expert – timber merchant, logger, cabinet maker or wood carver – can look at a tree & see the wood. See the colour difference between oak & ash, the grain, the knots formed by the branches. See the table, chair, floor or carved mouse into which it can be transformed.
Another kind of expert - forester, woodsman,tree surgeon - can control the kind of wood the tree will produce by judicious planting, pruning, thinning, watering & breeding.
For all I know a new breed of genetic arborists are on the verge of being able to produce a plank or block of wood to your speification, starting with just a single cell in a test tube.
It always depends on what you already know through learning & experience & which way round you are looking at it.
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The way to Ochtermurphy
The way to Ochtermurphy