Gospel Guidebook: Getting and Keeping It Right 
Quick Rebuttal of Andrew Fuller's Book "Strictures on Sandemanianism"
Introduction
Andrew Fuller's book "Strictures on Sandemanianism" (available here) seems to be the main source of people's knowledge of Robert Sandeman's teachings, even though anyone can read Robert Sandeman's writings for themselves using the Internet Archive (such as here). It has amazed me how many people on the Internet have blog posts criticizing Robert Sandeman (simply do a Google search for "Sandemanianism") when it seems quite obvious to me that they haven't read any of his writings. For example, as John Robbins discovered, two seminary trained contributors to the Banner of Truth website wrote critically of Robert Sandeman and Gordon Clark, despite neither of them having read Robert Sandeman's book and only one of them reading Gordon Clark's book on faith and saving faith (see here).
Robert Sandeman's Bare Persuasion
To put it simply, when Robert Sandeman speaks of justification through a bare persuasion of the truth, he is saying no other thing than what the Apostle John tells us in 1 John 5:9-10, "If we receive the witness of men, the witness of God is greater; for the witness of God is this, that He has borne witness concerning His Son. The one who believes in the Son of God has the witness in himself; the one who does not believe God has made Him a liar, because he has not believed in the witness that God has borne concerning His Son." Bare persuasion of the truth never looks to the workings of the Spirit inside a person for assurance of justification, for assurance is of the essence of what is believed, even as it says in Hebrews 11:1, "Now faith is the assurance of things hoped for, the conviction of things not seen." Bare persuasion of the truth gets assurance directly from the historical record of the Gospel itself, namely that Jesus Christ died for sinners and rose again, knowing that whoever believes (i.e., is persuaded by) this record has eternal life.
The Problem Created by Opponents of Sandeman
It is well known that Christians today are suffering from a crisis in assurance. Some of the greatest sufferers of lack of assurance are in the Reformed churches, despite having a correct understanding of the Gospel, including the active and passive obedience of Christ and double imputation. The reason for this is simple. It is possible to understand the Gospel and yet misunderstand what it means to believe the Gospel. Instead of the plain truth of 1 John 5:9-10 and Hebrews 11:1 quoted above, theologians like Andrew Fuller have replaced a bare persuasion of the truth with an elusive faith that involves what theologians called fiducia. For example, Louis Berkhof in his Systematic Theology describes fiducia as consisting in "personal trust in Christ as Saviour and Lord, including a surrender of the soul as guilty and defiled to Christ, and a reception and appropriation of Christ as the source of pardon and of spiritual life" (see here). Notice how carefully he worded this: "personal trust [that includes] a surrender..." Likewise, the Reformed confessions are to be blamed, for the confessions are ashamed of the the undecorated word "believe" and prefer to use mystical and ambiguous words like "resting," "hearty trust," and "upright faith." There is no excuse for this. The words "believe" and "belief" are the only and exclusive words used in salvific texts in the New Testament. And these words "believe" and "belief" are never modified with the adjectives "true," "sincere," "hearty," "lively," or "upright." By teaching a faith that involves fiducia and decorating it with modifiers, the Reformed churches are actually teaching a subtle form of mysticism, so it is no wonder that Reformed Christians are plagued by a lack of assurance. (And the only reason Sandeman gives the word "persuasion" the modifier "bare" is because he wants to make explicit that when he says "persuasion," he really means "persuasion" and not some theologically loaded word "persuasion" that differs in meaning from the standard everyday use of the word "persuasion." And he wouldn't even need to use the word "persuasion" if the standard everyday meaning of the words "belief" and "believe," such as described in 1 John 5:9-10, were not distorted beyond recognition by theologians.)
Quick Rebuttal of Andrew Fuller's book "Strictures on Sandemanianism"
Andrew Fuller, in his book "Strictures on Sandemanianism," exposes himself almost immediately as a mixer of faith and works. On pages 19-20 when he speaks against Sandeman's interpretation of Romans 4:5, he suggests that justification contains a transformative ethical element that includes a "conscious love to the divine character," and says that it must be proved "that by ungodly the apostle meant one who was at that time [of justification] an enemy of God." In order to debunk his assertion about justification containing a transformative ethical element, it is only necessary to provide the proof he requests. And it just so happens that I have already written extensively on this topic, proving that God justifies the ungodly while they are still in a state of ungodliness, thereby eliminating any transformative ethical element from justification (see, for example, here, here, and here). As a quick recap, it is only necessary to look at a couple texts, such as Romans 5:6-11 and Colossians 2:13. In Romans 5:6-11, the Apostle Paul uses present participles to describe the state of the ungodly when they were justified and reconciled at the cross. In particular, he describes them as "still being helpless," "still being sinners," and "being enemies." Likewise, in Colossians 2:13, he uses the present participle phrase "being dead in your trespasses and the uncircumcision of your flesh" to indicate that they were still dead in their trespasses when they were forgiven (which is a benefit contemporaneous with justification according to Romans 4:6-8) and were only ontologically changed and transformed in their nature subsequently when they were made alive. Henry Alford in his Greek New Testament Commentary recognized this by saying, "having forgiven (the aorist participle (which aor. 'having forgiven' is in English, we having but one past active participle) is here not contemporaneous with συνεζωοπ. [to make alive with] but antecedent" (see here)
Conclusion
And that's it. Fuller now has the proof he required. His system is debunked and Robert Sandeman has been vindicated. And if only the story could end here. But sadly, the errors of the past continue with us. When Martin Lloyd-Jones said that Fuller's book "more or less demolished Sandemanianism," it's too bad that he didn't have the insight to recognize that along with "demolishing Sandemanianism," he was also demolishing the true doctrine of justification by faith, and by taking away the key of knowledge, he also took away the key to assurance, leaving millions of Reformed Christians groping in the dark, searching for a spark of light within themselves, and never thinking to lift up their heads to see the blazing midday sun of the Gospel just above and outside of them.