briar-patch

Definitions

1. A dense thicket of thorny plants; ground made impassable by the impenetrable overgrowth of prickly vegetation.
   literally
2. An intellectual or philosophical issue abounding with seemingly unresolvable problems; a theoretical quandary or impasse.
   figuratively

Examples

“Hobbes: I'm sick of going over and through every obstacle on the hill. Calvin: Every obstacle?!? We missed the briar patch, didn't we?! Hobbes: By going down the gully and into the stream, yes.”

“I do not want⟳ to spend⟳ long in examining the arguments for this general deprecation of sense-perception or the intellectual motives for denying all credentials to sense-perception in order⟳ to enhance those of calculation, demonstration or religious faith. I want⟳ to get⟳ quickly to the much thornier briar-patch, the place⟳, namely, where scientific accounts of perception seem to issue⟳ in the consequential doctrine that observers, including the physiologists and psychologists themselves, never perceive what they naïvely suppose⟳ themselves to perceive.”

CEFR level