If Jesus only elects certain individuals for salvation, and then elects others for damnation (reprobation); from whence does someone’s assurance of salvation come from? How do they know that they are one of the elect for whom Christ has died, or for whom Christ has interceded (cf. Heb. 7:25)? This is a dilemma that one is presented with if you follow John Calvin’s view of double predestination, or any of the post Reformed orthodox, Calvinist theologians who followed Calvin and the Augustinian lead on this. It is this view of election and reprobation that Karl Barth critiqued thusly:
How can we have assurance in respect of our own election except by the Word of God? And how can even the Word of God give us assurance on this point if this Word, if this Jesus Christ, is not really the electing God, not the election itself, not our election, but only an elected means whereby the electing God—electing elsewhere and in some other way—executes that which he has decreed concerning those whom He has—elsewhere and in some other way—elected? The fact that Calvin in particular not only did not answer but did not even perceive this question is the decisive objection which we have to bring against his whole doctrine of predestination. The electing God of Calvin is a Deus nudus absconditus.
To be fair to Calvin, he was working from what David Gibson has identified in his published PhD dissertation Reading the Decree: Exegesis and Christology in Calvin and Barth following Richard Muller’s distinction between Barth and Calvin as: ‘soteriological christocentrism and principial christocentrism (Calvin follows the former).That notwithstanding, at a material level, Barth’s critique, I believe stands. If there is a decree that is ontologically distinct and outwith God’s life in Christ (as there is in Calvin), a decree (or a will in God that is not necessarily related to Jesus) by which God chooses some to salvation and reprobates others to damnation, then can we really ever look to Jesus for assurance of salvation? It would seem that instead, as Barth is noting, that we must look behind the back of Jesus to the decree itself in order to know whether or not we are truly saved. But this decree, impersonal as it is (and not necessarily or personally related to God’s life), cannot provide any real lively hope; only Jesus can.
I go with Barth’s critique of Calvin on this issue. It could be said at this fork in the road, that Calvin offers up a ‘God behind the back of Jesus.’ Meaning that there is an inaccessible decree, even through Jesus, that is determining the way that God chooses or not people for salvation. The decree is an abstraction, and thus not personally related to God in any meaningful way.
 Karl Barth, “CDII/2,” 111 cited by Oliver D. Crisp, “I Do Teach It, but I Also Do Not Teach It: The Universalism of Karl Barth (1886-1968),” in ed. Gregory MacDonald, All Shall Be Well: Explorations in Universalism and Christian Theology, from Origen to Moltmann (Eugene, OR: Cascade Books, 2011), 355.
 David Gibson, Reading the Decree: Exegesis and Christology in Calvin and Barth (London: T&T Clark A Continuum Imprint, 2009), 6. See the hyperlink to a post I have written that elaborates further on the definitional reality associated with this hermeneutical distinction between Barth and Calvin’s hermeneutics.
 This would fit well with Calvin’s voluntarism (i.e. that God’s will and commands or decrees are arbitrarily and thus non-necessarily related to God’s being/persons in relation. See the Stanford Encyclopedia of Philosophy for further explication of ‘voluntarism’.