Hi ChiaPet,
let me use a personal example. Before I came to realize that God is truly sovereign and his will cannot be frustrated by my will, and not I, but He is finally responsible for my salvation because I was chosen by him from eternity and his plan with me cannot fail, it was impossible for me to truly believe in the assurance of salvation which the Bible gives based on the fact that we are justified by faith alone, and There is therefore now no condemnation for those who are in Christ Jesus.” (Rom. 8:1 ESV). Since I believed that my will is determining my final position, I still allowed room for a future condemnation waiting for me in case I will apostatize. I sincerely believed that my present status of being justified is conditional and temporary, depending on my ability to keep my life in order. Consequently, because I allowed room for a future condemnation, I was not able to believe that now, in the present, there is “no condemnation”. Surely a condemnation was just around the corner if I would not hit the spiritual brakes in order to escape from an accident. There was no assurance that I’ll arrive safely at the destination, no assurance of salvation at all.
To be consistent, an Arminian has no assurance of salvation, because finally what determines his perseverance in faith is his own will, which is capricious, no guarantee of steadfastness. The heart is deceitful and causes us thousands of unexpected surprises. It is true that many Arminians today believe in assurance of salvation, but they are sustaining this position based on a blessed inconsistency with their basic premise, the freedom of the will.
The Arminian system of faith is unstable. Unstable because at any time people can fall on the side of denial of some essential parts of the gospel. The history proves that this is the case with the present situation of the evangelical world in which more and more voices are arguing for abandonment of the Sola Fide, Faith Alone principle of reformation. There are also denials of the imputation and penal substitution, all of these things following consequently the departure of the protestants from the reformed faith which they inherited from the first reformers.
Because of these and other considerations, fighting for Calvinism (which, by the way, was not peculiar to Calvin, but Luther, Zwingly, and the other reformers believed these doctrines) is a fight for stability in faith necessary for the preservation of the gospel. Because Arminian ideas are inconsistent with the gospel of justification by faith alone, through grace alone, even if the gospel is still believed in these circles, the instability inherent in these ideas leaves a door open to works righteousness.
Hope it helps
Gabriel