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Thanks for helping sort this out. Yes, of course, "every person has some operational assumptions about the nature of themselves or the world that undergird all action and thought." And "no one can question everything about themselves and the world all the time."

The issue here (for me at least) is not whether one has/uses "operational assumptions" but rather what assumptions one has about those or any other operational assumptions. A foundationalist (according to Grobstein) assumes that some set of operational assumptions, either the ones currently being used or ones that one aspires to find, have the status of fixed, eternal "Truth." A non-foundationalist (according to Grobstein, Rorty, and others) assumes that all assumptions, existing as well as yet to be conceived, are rooted in human experiences to date ("explanations for things in the world ... involve things in the world, not outside of it") and so are, in principle, subject to future revision.

Does it matter, whether one is a foundationalist or a non-foundationalist in these terms? Does it affect how one does science? reads literature? interacts with other people? I think it does, but we'll see ...