We used to teach that an imperative built on the present tense stem indicated an action already underway. This is most evident in prohibitions, for example, to tell a barking dog to stop. We know this is no longer the case, but it does surface from time to time in translations and commentaries.
The Pharisees wanted to know if Jesus believed divorce was legitimate for any and all reasons. The challenge is to translate the phrase, recognizing that it is a singular (each individual reason) and also general (any and all reasons).
Translators have to be careful with the nuances of the words they use. Did Jesus “notice” the other eleven disciples, or was be “looking” at them when he rebuked Peter? It creates an odd picture to not look at the person you are speaking to, and ὁράω can mean to “notice.”