I can perceive you can perceive he can perceive we can perceive you can perceive they can perceive
V-ing form
I can be perceiving you can be perceiving he can be perceiving we can be perceiving you can be perceiving they can be perceiving
Perfect
I can have perceived you can have perceived he can have perceived we can have perceived you can have perceived they can have perceived
V-ing perfect
I can have been perceiving you can have been perceiving he can have been perceiving we can have been perceiving you can have been perceiving they can have been perceiving
Negation
Simple form
I cannot perceive you cannot perceive he cannot perceive we cannot perceive you cannot perceive they cannot perceive
V-ing form
I cannot be perceiving you cannot be perceiving he cannot be perceiving we cannot be perceiving you cannot be perceiving they cannot be perceiving
Perfect
I cannot have perceived you cannot have perceived he cannot have perceived we cannot have perceived you cannot have perceived they cannot have perceived
V-ing perfect
I cannot have been perceiving you cannot have been perceiving he cannot have been perceiving we cannot have been perceiving you cannot have been perceiving they cannot have been perceiving
Interrogative form
Simple form
can I perceive? can you perceive? can he perceive? can we perceive? can you perceive? can they perceive?
V-ing form
can I be perceiving? can you be perceiving? can he be perceiving? can we be perceiving? can you be perceiving? can they be perceiving?
Perfect
can I have perceived? can you have perceived? can he have perceived? can we have perceived? can you have perceived? can they have perceived?
V-ing perfect
can I have been perceiving? can you have been perceiving? can he have been perceiving? can we have been perceiving? can you have been perceiving? can they have been perceiving?
Interro-negative form
Simple form
can I not perceive? can you not perceive? can he not perceive? can we not perceive? can you not perceive? can they not perceive?
V-ing form
can I not be perceiving? can you not be perceiving? can he not be perceiving? can we not be perceiving? can you not be perceiving? can they not be perceiving?
Perfect
can I not have perceived? can you not have perceived? can he not have perceived? can we not have perceived? can you not have perceived? can they not have perceived?
V-ing perfect
can I not have been perceiving? can you not have been perceiving? can he not have been perceiving? can we not have been perceiving? can you not have been perceiving? can they not have been perceiving?