The grammar as a map

The axis is time. On the left, what was already over when the events being told happened; in the middle, now; on the right, what is still to come. Each tense hangs at the point it says something about — “future” is not a chapter heading here but a stop, the same stop at which each language puts something different.

Below it are the forms that cannot sit at any stop. A future form for a guess, a past form for politeness, a conditional whose form is dictated by the condition: the name then says nothing about the point in time, and that is not a special case but half the reason tenses are hard.

Press a level to show only that level; press it again to bring everything back.

Now the level is the axis: from 1 to 4, one band per level, with the areas stacked beneath one another. So one picture shows what each level adds to each area — “what does B1 add to the verb?” cannot be answered at a glance anywhere else.

An empty cell is information, not a gap: that there is nothing on the passive at 1 is part of the picture.