Sorrow is knowledge:  they who know the most
Must mourn the deepest o’er the fatal truth,
The tree of knowledge is not that of life. 
Philosophy and science and the springs
Of wonder, and the wisdom of the world
I have essayed, and in my mind there is,
A power to make these subject to itself.

He is engaged in calling spirits; and, as the incantation proceeds, they obey his bidding, and ask him what he wants; he replies, “forgetfulness.”

FIRST SPIRIT

Of what—­of whom—­and why?

MANFRED

Of that which is within me; read it there——­
Ye know it, and I cannot utter it.

SPIRIT

We can but give thee that which we possess;—­
Ask of us subjects, sovereignty, the power
O’er earth, the whole or portion, or a sign
Which shall control the elements, whereof
We are the dominators.  Each and all—­
These shall be thine.

MANFRED

Oblivion, self oblivion—­
Can ye not wring from out the hidden realms
Ye offer so profusely, what I ask?

SPIRIT

It is not in our essence, in our skill,
But—­thou may’st die.

MANFRED

   Will death bestow it on me?

SPIRIT

We are immortal, and do not forget;
We are eternal, and to us the past
Is as the future, present.  Art thou answer’d?

MANFRED

Ye mock me, but the power which brought ye here
Hath made you mine.  Slaves! scoff not at my will;
The mind, the spirit, the Promethean spark,
The lightning of my being is as bright,
Pervading and far darting as your own,
And shall not yield to yours though coop’d in clay. 
Answer, or I will teach you what I am.

SPIRIT

We answer as we answer’d.  Our reply
Is even in thine own words.

MANFRED

Why say ye so?

SPIRIT

If, as thou say’st, thine essence be as ours,
We have replied in telling thee the thing
Mortals call death hath naught to do with us.

MANFRED

I then have call’d you from your realms in vain.

This impressive and original scene prepares the reader to wonder why it is that Manfred is so desirous to drink of Lethe.  He has acquired dominion over spirits, and he finds, in the possession of the power, that knowledge has only brought him sorrow.  They tell him he is immortal, and what he suffers is as inextinguishable as his own being:  why should he desire forgetfulness?—­Has he not committed a great secret sin?  What is it?—­He alludes to his sister, and in his subsequent interview with the witch we gather a dreadful meaning concerning her fate.  Her blood has been shed, not by his hand nor in punishment, but in the shadow and occultations of some unutterable crime and mystery.