Although I do not accept Calvinism as reflective of God or his plan of salvation as depicted in Scripture, I do maintain the following. Whether God chose to save man according to the teachings of Calvinism or Extensivism, salvation is all by grace. I further believe he could have chosen either way; since, in either scenario, he would have sovereignly and freely chosen the plan including all of its components, each would be totally by grace; however, most Calvinists are not so kind regarding the possibility of Extensivism.
When discussing Calvinism and Extensivism, Calvinists often portray Calvinism as beginning with God (God’s decision) and Extensivism as beginning with man (man’s decision). This juxtaposition easily positions Calvinism as originating in and dependent upon God, and Extensivism originating in and dependent upon man; even worse, it either explicitly or strongly implies God is, at least in some sense, dependent upon man.
Commenting on Calvinism, Millard Erickson says, “Calvinists believe that God’s plan is logically prior and that human decisions and actions are a consequence.”  Erickson’s emphasis here is upon God’s determinism, which Calvinists seem to believe is the only way to position God’s plan (decision) as existing before man’s action (decision), and therefore making man dependent upon God. In explaining Arminianism’s view, Erickson says, “Thus, those whom God foreknew would believe are those he decided would be saved. . . . God knows what all of us are going to do. He, therefore, wills what he foresees will happen. Note that human action and its effects are not a result of God’s decision. The human action is logically prior. It is humans who render their actions certain; God simply acquiesces“ (italics added).
In reality, according to Extensivism, God did not merely “forese” man’s choice and what “will happen” as a consequence of man’s choice any more than God foresaw man would have the ability to choose otherwise and create various possibilities. Rather, as an essentially omniscient being who eternally knows himself exhaustively which includes his intentions, God chose to create man in his image with the ability and freedom to choose otherwise in various states of affairs that God determined he could. Libertarian freedom does not require that every event be the result of otherwise choice but only that one or more are; we call these contingencies.
This understanding reflects a more accurate view of Extensivism, wherein God is not dependent upon man; nor does he learn perceptively (foreseeing or looking outside of himself or learn sequentially), and therefore merely “acquiesces.” Rather, man is a being God created with otherwise choice, and he operates as such when and where God has determined he can; hence, man is dependent upon God, and God is, at every second and juncture, sovereign.
Therefore Erickson’s statement “Thus, those whom God foreknew would believe are those he decided would be saved” is backward and therefore in error. Correctly stated, it is that God decided he would create man with the ability to believe or not (exercise otherwise choice), and post-fall he would grace enable fallen man to be able to believe or not. This decision entailed that his relationship with man would be one in which man could choose to respond or reject and that he would save those whom he knew would believe, which he always knew as an essentially omniscient being. Thus, God’s decision is logically prior to man’s decision to believe in contrast to Erickson’s (as well as most Calvinist’s) portrayal.
To wit, according to Calvinism, God knew what man would do because he always knew he would micro-determine every thought and act of man and what that would entail. Whereas according to Extensivism, God knew what man would be, do, and what that would entail because God chose to create man in that way, and he is an intrinsically omniscient being. In both views, God’s decision is logically prior to man’s decision, and he knew every sequence and consequence of his plan without looking outside of himself.
Examples of God granting otherwise choice permeate the Scripture. For example, Adam (Gen 2:16-17), the choice of being blessed or curse (Deut 30:15-18), to serve God or not (Josh 24:15), or to believe unto salvation or not (John 3:18). He also brings about events that are not wrought by the actions of man (Dan 9:24-27; Rev 6, 20-22), as well as determining the time allotted to man in various states of affairs. At times, God overrides man’s otherwise choice (Dan 4:25), which only temporarily suspends man’s libertarian freedom; it does not eliminate it permanently.
Consequently, we see that Extensivism begins with God; he alone, by his sovereign grace, decided what his salvific plan entails and what abilities and options he affords man. For example, would his plan entail man is determined, having no otherwise choice (Calvinism), or would his plan entail man is not determined, making grace-enabled otherwise choices (Extensivism)? In either scenario, both would eternally exist in the mind of God.
Therefore, whether God would include in his salvific plan the inability to exercise otherwise choice or the ability to exercise otherwise choice does not change the fact that every aspect of salvation is all according to God’s sovereign determination and grace, and therefore totally dependent on and under God’s sovereignty. That is to say, no one merits salvation nor is any act regarding salvation less of grace merely because of the abilities God affords man or the order of some sequential components like choice, consequence, or faith and regeneration.
This proper understanding of Extensivism means it is illegitimate to characterize Extensivism as somehow beginning with man, making God dependent on man in which he “acquiesces,” or involving works, merit, or virtue as the genesis of faith since salvation in both belief systems begin in the eternal, omniscient mind and will of God as well as in time. Man’s salvation is also sustained by and reaches ultimate sanctification through grace. To wit, if grace provides all the details of salvation, then salvation cannot be justifiably dismissed as a meritorious accomplishment of man, thereby diminishing God’s glory in salvation. To do so is to obfuscate the facts and refuse to acknowledge the amazing grace of each perspective.
 For an explanation of logical and temporal priority see my article, “Why Calvinists Attempts to Make Regeneration Logically Prior and Not Temporally Prior Fails,” http://wmh.24c.myftpupload.com/2018/11/12/why-calvinists-attempt-to-make-regeneration-logically-prior-and-not-temporally-prior-fails/.
 Millard J. Erickson, Christian Theology, 3rd ed. Logos ed. (Grand Rapids, MI: Baker Academic, 2013), 326.
 Ibid., 327.