In an earlier post (Link) I provided a short quote from Thomas Grantham on the extent of the atonement, which I first read in J Matthew Pinson's article, Thomas Grantham’s Theology of the Atonement and Justification. Here is the full section from Thomas Grantham's 1678 work, Christianismus Primitivus :
According to the Will of God, and his Eternal Wisdom, Christ did, in the place and stead of Mankind, fulfil that Law, by which the whole World stood guilty before God.
How deeply Mankind stood indebted to the Righteous God of Heaven and Earth, and how unable he was to pay that score; and how consequently he must inevitably undergo the eternal displeasure of God, with the malediction of his Righteous Law, is excellently set forth, Rom. 3. 9, &c. Are we better than they? No in no wise: for we have before charged both Jews and Gentiles, that they are all under sin; As it is written, there is none Righteous, no not one.—They are all gone out of the way, they are altogether unprofitable, there is none that doth good, no not one. — Now we know, that what things soever the Law saith, it saith to them that are under the Law; that every Mouth may be stopped, and all the World may become subject to the Judgment of God. Therefore by the Deeds of the Law shall no flesh be justified in the sight of God; for by the Law, is the knowledge of Sin. So then, we see there is a Law, by which the whole World stands Guilty; and upon that account, subject to the Judgment of God. It matters not then for the Mode, or Circumstances, under which the Law is given, they both fall short before God. He hath therefore shut up all in Unbelief, or concluded all under Sin; and surely we may conclude, it is, that he may magnify his Mercy unto all, even to the whole World in this case, as well as to the Jews, Rom. 11. 32.
And as he, even so we, have reason to ascribe Wisdom to God, for it hath appeared Wonderfully; he having designed to magnify his Mercy in Christ, as the only Physician to Cure the Malady of Mankind, would certainly provide a Plaister commensurable with the Sore, that none may cry out and say, I am undone, I am wounded with the unavoidable wound of Mankind: And there is no Balm for me, the Physician hath made the Plaister too narrow, that Thousands, and ten Thousands, cannot possibly have Healing by it; nay, he hath determined to see us perish without any Remedy. Alas! there is none to save us, neither could we come whole and sound into the World; we are born to be destroyed, and destroyed we must be. To quell which hideous (and indeed most just) complaint (if indeed God had not in his Wisdom provided Relief for them): Behold, thus saith the Lord, Isa. 45.22. Look unto me, and be ye saved all the ends of the Earth: for I am God, and there is none else. Therefore seek to me, and none but me, and ye shall be saved: for I am God; even such a God as delight to save, but not to destroy. Ezek. 18. 23. Have I any pleasure at all in the death of the Wicked? This is good and acceptable in the sight of God our Saviour; who will have all Men to be saved, and come to the knowledge of the truth, I Tim. 2.3,4.
When we are bid to behold the Lamb of God, which taketh away the Sins of the World, John 1.29. are we to except any Person in the World, or the greatest part of the World? God forbid. Are they all become guilty per force (except Adam) and have none to justify them? Where is then the Lamb? Behold, here is Fire, the Wood, and the Knife, but where is the Sacrifice, may many say, if indeed the Lamb of God died not for them? But the Holy Ghost resolves the Query to the full, 1 John 2.1. He is the Propitiation for our Sins, and not for ours only, but also for the Sins of the whole World.
Acts 17. The Apostle speaking of Mankind, indefinitely declares that they are all the Off-spring of God. And can we think that he will harden himself (like the Estridg) against his Off-spring, as though they were not his? We which are evil by Nature, would not so deal with our Off-spring; and surely God transcends us in all Goodness whatsoever.
Under the Parable of the Creditor, and the two Debtors, Luke 7.40. may fitly be understood Jew and Gentile, even whole Mankind; and some Expositors do take it so. Now they were both in one Predicament in this; they had nothing to Pay, though the Debt was not equal. Now the Kingdom of Heaven is compared to him that takes an account of Persons thus engaged, Mat. 18.21. to 28. Now, saith our Saviour, when they had nothing Pay, he frankly forgave them both, viz. caused the Bond to be cancelled by which they stood obliged, nailing it to his Cross; requiring them in their Capacity, to do likewise one unto another, and to love him.
And from hence, that all Men are bound to love Christ, as their indispensable duty, under pain of Anathema, or Execration; Maran-atha, till the Lord come (or, as some) even for ever, I Cor. 16. 22. Hence we justly infer, that God in Love gave Christ for all Men, even to bless them, in turning every one of them away from their Iniquities, Acts 3. ult. And shew me the Man which ought not to love Christ, and then I will shew the Man whom Christ did not love. But if all Men are bound to love him, then it’s certain the Will of God was, that his Love should extend to them: For we love him, because he first loved us. And herein is Love, not that we loved God, but God loved us, and sent his Son to be a Propitiation for our Sins, I John 4. 10, 19. And again, herein perceive we the Love of God, because he laid down his Life for us. The result is this, whom God loved, them Christ died for. All that Christ died for, ought to love him; but all Men ought to love him. Ergo, God loved, and Christ died for all Men, who hath therefore obliterated the condemning power of the Law, by which they were indebted to him; so that according to the Will of God, and his Eternal Wisdom, the Door of Salvation is opened to them, and they exhorted to enter therein with thanksgiving, Psal. 100. 1, 2, 3, 4.
 Thomas Grantham, Christianismus Primitivus: or, The ancient Christian religion, in its nature, certainty, excellencey, and beauty (internal and external) particularly considered, asserted, and vindicated, from the many abuses which have invaded that sacred profession (London, 1678), Book II, 62-64, (online: Link). I have updated some of the spelling for readability.