The assay

Immediately after the invocation to Book III, God is presented as seeing Adam, then Satan, then the result of Satan's "assay:"

Through all restraint broke loose he wings his way
Not farr off Heav'n, in the Precincts of light,
Directly towards the new created World,
And Man there plac't, with purpose to assay [ 90 ]
If him by force he can destroy, or worse,
By some false guile pervert; and shall pervert
For man will heark'n to his glozing lyes,
And easily transgress the sole Command,
Sole pledge of his obedience:

"Assay" is cognate with "essay," both carrying the idea of to try, to test:

as·say

Pronunciation: \ˈa-ˌsā, a-ˈsā\

Function: noun

Etymology: Middle English, from Anglo-French assai, essai — more at essay

Date: 14th century

1 archaic : trial, attempt

2 : examination and determination as to characteristics (as weight, measure, or quality)

3 : analysis (as of an ore or drug) to determine the presence, absence, or quantity of one or more components; also : a test used in this analysis

4 : a substance to be assayed; also : the tabulated result of assaying.

Assay is a technical term in Alchemy as well:

"Fire Assaying is an ancient and time-honored Art/Science which determines the precious metal content in ores, metallics, solutions and all other materials bearing Gold and Silver. It is a branch of analytical, inorganic chemistry which has as its object the quantitative determination of values in small amounts of material which represent much larger amounts of the same material.

. . . the non-precious, or base metals are Oxidized away, leaving the precious metals behind.

The Fire Assay method, which is still most widely viewed as the most accurate means of determining Gold and Silver content, has been altered very little over the centuries. Its origins can be traced as far back as the Bible:"

I have made you an assayer and tester among my people
That you may know and assay their ways
They are bronze and iron, and they act corruptly
The bellows blow fiercely, and the lead is consumed by the fire
In vain the refining goes on; refuse silver they are called
For the Lord has rejected them*

(*This interesting alchemical translation of Jeremiah 6.27 ff courtesy of a contemporary metals assayer.)

Is it fanciful to see a continuation of the alchemical process a little further on, when God the Father foretells the Last Judgment, the consignment of human dross to death, and the purgation of creation in fire?

Then all thy Saints assembl'd, thou shalt judge [ 330 ]
Bad men and Angels, they arraignd shall sink
Beneath thy Sentence; Hell her numbers full,
Thenceforth shall be for ever shut. Mean while
The World shall burn, and from her ashes spring
New Heav'n and Earth, wherein the just shall dwell [ 335 ]
And after all thir tribulations long
See golden days, fruitful of golden deeds,
With Joy and Love triumphing, and fair Truth.