There's truth as far as you knows it; and there's truth as far as you're asked for it. But they don't represent the whole truth - not necessarily.
A half-truth masquerading as the whole truth becomes a complete untruth.
All I have told is true, but it is not the whole truth.
Faith has need of the whole truth.
It takes the whole church to know the whole truth.
Don't lie, but don't tell the whole truth.
Poetry implies the whole truth, philosophy expresses only a particle of it.