"A new idea is delicate. It can be killed by a sneer or a yawn; it can be stabbed to death by a quip and worried to death by a frown on the right man’s brow." -Charles Brower
Your internal censor is the process that inhibits you from proposing absurd solutions to problems (and prevents you from saying what you think in general). Turning down the volume on the internal censor greatly assists brainstorming, as most people have it set very high for normal day to day use. Practices such as cultivating a playful environment, feeling of safety, saying or writing whatever comes to mind as quickly as possible (stream of consciousness writing), are all intended to tone down the internal censor. Many people find improv games useful for this purpose as well.
Many initially absurd solutions turn out to either be usable, have usable components, or highlight some area of the problem or method of inquiry that is helpful.