I could theorise you could theorise she could theorise we could theorise you could theorise they could theorise
V-ing form
I could be theorising you could be theorising she could be theorising we could be theorising you could be theorising they could be theorising
Perfect
I could have theorised you could have theorised she could have theorised we could have theorised you could have theorised they could have theorised
V-ing perfect
I could have been theorising you could have been theorising she could have been theorising we could have been theorising you could have been theorising they could have been theorising
Negation
Simple form
I couldn't theorise you couldn't theorise she couldn't theorise we couldn't theorise you couldn't theorise they couldn't theorise
V-ing form
I couldn't be theorising you couldn't be theorising she couldn't be theorising we couldn't be theorising you couldn't be theorising they couldn't be theorising
Perfect
I couldn't have theorised you couldn't have theorised she couldn't have theorised we couldn't have theorised you couldn't have theorised they couldn't have theorised
V-ing perfect
I couldn't have been theorising you couldn't have been theorising she couldn't have been theorising we couldn't have been theorising you couldn't have been theorising they couldn't have been theorising
Interrogative form
Simple form
could I theorise? could you theorise? could she theorise? could we theorise? could you theorise? could they theorise?
V-ing form
could I be theorising? could you be theorising? could she be theorising? could we be theorising? could you be theorising? could they be theorising?
Perfect
could I have theorised? could you have theorised? could she have theorised? could we have theorised? could you have theorised? could they have theorised?
V-ing perfect
could I have been theorising? could you have been theorising? could she have been theorising? could we have been theorising? could you have been theorising? could they have been theorising?
Interro-negative form
Simple form
couldn't I theorise? couldn't you theorise? couldn't she theorise? couldn't we theorise? couldn't you theorise? couldn't they theorise?
V-ing form
couldn't I be theorising? couldn't you be theorising? couldn't she be theorising? couldn't we be theorising? couldn't you be theorising? couldn't they be theorising?
Perfect
couldn't I have theorised? couldn't you have theorised? couldn't she have theorised? couldn't we have theorised? couldn't you have theorised? couldn't they have theorised?
V-ing perfect
couldn't I have been theorising? couldn't you have been theorising? couldn't she have been theorising? couldn't we have been theorising? couldn't you have been theorising? couldn't they have been theorising?