English verb conjugation
COULD EXIST

Regular verb: exist - existed - existed

Affirmation

Simple form	V-ing form
I could exist you could exist she could exist we could exist you could exist they could exist	I could be existing you could be existing she could be existing we could be existing you could be existing they could be existing
Perfect	V-ing perfect
I could have existed you could have existed she could have existed we could have existed you could have existed they could have existed	I could have been existing you could have been existing she could have been existing we could have been existing you could have been existing they could have been existing

Negation

Simple form	V-ing form
I could not exist you could not exist she could not exist we could not exist you could not exist they could not exist	I could not be existing you could not be existing she could not be existing we could not be existing you could not be existing they could not be existing
Perfect	V-ing perfect
I could not have existed you could not have existed she could not have existed we could not have existed you could not have existed they could not have existed	I could not have been existing you could not have been existing she could not have been existing we could not have been existing you could not have been existing they could not have been existing

Interrogative form

Simple form	V-ing form
could I exist? could you exist? could she exist? could we exist? could you exist? could they exist?	could I be existing? could you be existing? could she be existing? could we be existing? could you be existing? could they be existing?
Perfect	V-ing perfect
could I have existed? could you have existed? could she have existed? could we have existed? could you have existed? could they have existed?	could I have been existing? could you have been existing? could she have been existing? could we have been existing? could you have been existing? could they have been existing?

Interro-negative form

Simple form	V-ing form
could I not exist? could you not exist? could she not exist? could we not exist? could you not exist? could they not exist?	could I not be existing? could you not be existing? could she not be existing? could we not be existing? could you not be existing? could they not be existing?
Perfect	V-ing perfect
could I not have existed? could you not have existed? could she not have existed? could we not have existed? could you not have existed? could they not have existed?	could I not have been existing? could you not have been existing? could she not have been existing? could we not have been existing? could you not have been existing? could they not have been existing?