Calvin missed this aspect of Foreknowledge

KJV Deuteronomy 32:4 He is the Rock, his work is perfect: for all his ways are judgment: a God of truth and without iniquity, just and right is he.

One of the just and right judgments of God was Predestination of the Elect unto salvation.

“How is God just and right,” someone might ask, “when He said all have the Free Will choice of life or death (De 30:19 cp Ge 4:7), but in fact God had already predestined all who would be saved, even before the world began, and not according to any choice they made in this life. (Eph 1:5; 2:8)?

Paul’s words supply the answer, but we must deduce it.

Ro 8:29 For whom he did foreknow, he also did predestinate to be conformed to the image of his Son, that he might be the firstborn among many brethren.-kjv

Did “foreknow” (proginosko) is “to know before,” did “predestine” (proorizo) is to “foreordain.” Foreknowing is coordinate with predestinating, naturally read, the first causes the second.

Should we violate Ockham’s razor and view this “not as metaphysically true, but in concession to human limitations of thought” (Vincent, Word Studies in the New Testament, Bellingham, WA), or allow parsimony dictate as it is the common characteristic evident in correct interpretation?

Accepting the natural reading doesn’t contradict salvation by grace alone as it is clear God already knows who are His, none of the foreknown fail to be conformed to Jesus.

So nothing said so far contradicts salvation by grace alone:

Ephesians 2:5-9 5 Even when we were dead in sins, hath quickened us together with Christ, (by grace ye are saved;) 6 And hath raised us up together, and made us sit together in heavenly places in Christ Jesus: 7 That in the ages to come he might shew the exceeding riches of his grace in his kindness toward us through Christ Jesus. 8 For by grace are ye saved through faith; and that not of yourselves: it is the gift of God: 9 Not of works, lest any man should boast.

“Paul elaborated, And this is not from yourselves, it is the gift of God. Much debate has centered around the demonstrative pronoun “this” (touto). Though some think it refers back to “grace” and others to “faith,” neither of these suggestions is really valid because the demonstrative pronoun is neuter whereas “grace” and “faith” are feminine. Also, to refer back to either of these words specifically seems to be redundant. Rather the neuter touto, as is common, refers to the preceding phrase or clause. (In Eph. 1:15 and 3:1 touto, “this,” refers back to the preceding section.) Thus it refers back to the concept of salvation (2:4-8a), whose basis is grace and means is faith. This salvation does not have its source in man (it is “not from yourselves”), but rather, its source is God’s grace for “it is the gift of God.” –Walvoord, John F. The Bible Knowledge Commentary, Victor Books (Wheaton, IL), 1983-1985.

So what was this foreknowing for if it’s not for God’s benefit?

There are scriptural parallels to God knowing His own perfectly, yet He still tests their loyalty:

Psalm 11:
4 The LORD is in his holy temple, the LORD'S throne is in heaven: his eyes behold, his eyelids try, the children of men.
5 The LORD trieth the righteous: but the wicked and him that loveth violence his soul hateth.
6 Upon the wicked he shall rain snares, fire and brimstone, and an horrible tempest: this shall be the portion of their cup.
7 For the righteous LORD loveth righteousness; his countenance doth behold the upright.

Job 23:10 But he knoweth the way that I take: when he hath tried me, I shall come forth as gold.

So why does God test those He already knows are His? The answer is in the book of Job, such tests occur for the benefit of others:

KJV Job 1:6 Now there was a day when the sons of God came to present themselves before the LORD, and Satan came also among them….9 Then Satan answered the LORD, and said, Doth Job fear God for nought?

Hence, tests of loyalty occur so that angelic observers can see for themselves God is not wrong about who are His.

But what of the wicked? Note God doesn’t know them with the upright:

Ps 37:18-20
18   The LORD knoweth the days of the upright: and their inheritance shall be for ever.
19   They shall not be ashamed in the evil time: and in the days of famine they shall be satisfied.
20   But the wicked shall perish, and the enemies of the LORD shall be as the fat of lambs: they shall consume; into smoke shall they consume away.

Nahum 1:7-8
7   The LORD is good, a strong hold in the day of trouble; and he knoweth them that trust in him.
8   But with an overrunning flood he will make an utter end of the place thereof, and darkness shall pursue his enemies.=kjv

Evidently the wicked are irrelevant to God, as He is good. Therefore God doesn’t want to know them, and so they perish.

So where am I going with this?

Suppose two blind men were describing the same elephant. The one feeling the tail seems to contradict the one touching its ears. But to the one viewing the entire elephant, the contrary statements make perfect sense.

So Paul has in mind a much greater construct than anything proposed by either Pelagius or Calvin. Its not free will versus Election by grace, its God knowing who are His, but choosing to reveal the rightness of that choice to all who might wonder.

Consistent with this construct, the verb proginosko means God “knew these before.”

Before what? Their existence? Nothing that exists does so apart from God or His knowing. God is omnipresent, He fills all things, including Eternity (Is 57:15). God cannot be contained by time and space, the very existence of that is dependant upon Him (1 Ki 8:27; Col 1:15). Hence we read Eph 2:6 “made us sit in heavenly places” or Re. 13:8 “Lamb slain from the foundation of the world.”)

So there is no “before” God’s knowing, for anything that exists.

However contingencies, “what if” scenarios which never achieve objective existence, can be objects of God's foreknowledge.

So the data leads naturally to this conclusion, God already knew all who are His, but chose to put them to the test, in a contingency that evidenced the rightness of their election: When their will was truly free, they chose God.

This was done for the benefit of creation, not for Him. He already knows who are His.

Lest God’s Elect, whether human or angelic (1 Ti 5:21), mourn the non selection of loved ones, God reveals via foreknowledge why some were selected so all questions about this can be answered. It would be an act of kindness not to foreknow the non elect, as then the full measure of their evil is known only to God.

God offers salvation to those not selected, but these never take Him up on His offer:

KJV Genesis 4:7 If thou doest well, shalt thou not be accepted? and if thou doest not well, sin lieth at the door. And unto thee shall be his desire, and thou shalt rule over him.

KJV Matthew 13:15 For this people's heart is waxed gross, and their ears are dull of hearing, and their eyes they have closed; lest at any time they should see with their eyes, and hear with their ears, and should understand with their heart, and should be converted, and I should heal them.

So all creation will see the Judgments of God:

KJV Revelation 15:4 Who shall not fear thee, O Lord, and glorify thy name? for thou only art holy: for all nations shall come and worship before thee; for thy judgments are made manifest.

It was God’s good pleasure and will to save the Elect, and do so in a way that would allow them to enjoy eternity even though some of their loved ones weren’t selected.

KJV Deuteronomy 32:4 He is the Rock, his work is perfect: for all his ways are judgment: a God of truth and without iniquity, just and right is he.

Probably God chose not to "foreknow" the non elect, to protect His elect from viewing just how evil the non elect could be.

It is written:

KJV 1 John 3:8 …For this purpose the Son of God was manifested, that he might destroy the works of the devil.

This means none of God’s elect will be lost, otherwise the devil’s work wasn’t destroyed.

It follows from all that is revealed about our Loving God, that if even one of His Elect were lost, God would mourn their absence for all eternity. Therefore we can be certain, not a hair upon their head will be lost.

Romans 11:26 And so all Israel shall be saved: as it is written, There shall come out of Sion the Deliverer, and shall turn away ungodliness from Jacob: 27 For this is my covenant unto them, when I shall take away their sins.