A failure of imagination usually refers to a bad outcome which, despite being predictable, is not imagined and thus not planned for. However, I use the expression in a more positive light, to speak of a good outcome that, despite being possible, is not imagined and thus not explored. I know of two failures of imagination:

The first failure of imagination is imagining that something is impossible without actual proof. Even given proof that something is impossible, one should be attentive to the hypotheses that went into the proof, as well as to what exactly has been proven impossible1.

The second failure of imagination is doing things the way everyone else does because you do not even realize that there is another way.

  1. I learned how to prove that something is not possible using math. Then, engineering taught me that something being impossible usually just meant that I needed to consider a larger set of tools or a finer definition of the problem I wanted solved. Most things are possible up to an acceptable threshold. ↩︎