Misunderstandings

If such a thing had been my thought,
I should have told you so before,
But as I didn't, then you ought
To ask for such a thing no more,
For to teach one who has been taught
Is always thought an awful bore.

Now to commence my argument,
I shall premise an observation,
On which the greatest kings have leant
When striving to subdue a nation,
And e'en the wretch who pays no rent
By it can solve a hard equation.

Its truth is such, the force of reason
Can not avail to shake its power,
Yet e'en the sun in summer season
Doth not dispel so mild a shower
As this, and he who sees it, sees on
Beyond it to a sunny bower-
No more, when ignorance is treason,
Let wisdom's brows be cold and sour.