If I had to pick just one idea from the field of resilience engineering that has influenced me the most, it would be David Woods’s notion of the adaptive universe. In his 2018 paper titled The theory of graceful extensibility: basic rules that govern adaptive systems, Woods describes the two assumptions  of the adaptive universe:
- Resources are always finite.
- Change is ongoing.
That’s it! Just two simple assertions, but so much flows from them.
At first glance, the assumptions sound banal. Nobody believes in infinite resources! Nobody believes that things will stop changing! Yet, when we design our systems, it’s remarkable how often we don’t take these into account.
The future is always going to involve changes to our system that we could not foresee at design time, and those changes are always going to be made in a context where we are limited in resources (e.g., time, headcount) and hence will have to make tradeoffs. Instead, we tell ourselves a story about how next time, we’re going to build it right. But, we aren’t, because the next time we’ll also be resource constrained, and so we’ll have to make some decisions for reasons of expediency. And the next time, the system will also change in ways we could never have predicted, invalidating our design assumptions.
Because we are forever trapped in the adaptive universe.
 If you watch Woods’s online resilience engineering short course, which precedes this paper, he mentions a third property: surprise is fundamental. But I think this property is a consequence of the first two assumptions rather than requiring an additional assumption, and I suspect that’s why he doesn’t mention it as an assumption in his 2018 paper.