To underpin is to justify or support the ideas behind something, the way your extensive research underpins your self-published book on ice cream trucks in the United States.

Whenever you substantiate someone’s claims, theories, or stories, you underpin them. A slightly different way to underpin is to form the basis or foundation of something: “A philosophy of empathy and kindness underpins all the interactions at my wonderful summer camp.” This verb can also be used in a more literal way, to mean “support from below,” the way the foundation of a house underpins everything that’s built on top of it.

Definitions of underpin
  1. verb

    support with evidence or authority or make more certain or confirm

    bear out, corroborate, support
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    type of:

    agree, check, correspond, fit, gibe, jibe, match, tally

    be compatible, similar, or consistent; coincide in their characteristics

  2. verb

    support from beneath

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    type of:

    hold, hold up, support, sustain

    be the physical support of; carry the weight of

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