Monergism

The ground of discrimination that exists among men is the sovereign will of God and that alone; but the ground of damnation to which the reprobate are consigned is sin and sin alone.
John Calvin

Moreover, Holy Scripture most especially highlights this eternal and undeserved grace of our election and brings it out more clearly for us, in that it further bears witness that not all people have been chosen but that some have not been chosen or have been passed by in God's eternal election - those, that is, concerning whom God, on the basis of his entirely free, most just, irreproachable, and unchangeable good pleasure, made the following decision: to leave them in the common misery into which, by their own fault, they have plunged themselves; not to grant them saving faith and the grace of conversion; but finally to condemn and eternally punish them (having been left in their own ways and under his just judgment), not only for their unbelief but also for all their other sins, in order to display his justice. And this is the decision of reprobation, which does not at all make God the author of sin (a blasphemous thought!) but rather its fearful, irreproachable, just judge and avenger.
Canons of Dort (1:15)

Predestination & Reprobation Contrasted
R.A. Finlayson

1. [The Scripture] does not teach or imply a double predestination. In an attempt to distinguish between election and reprobation we should use predestination for the elect and foreordination for the reprobate.

2. Election and reprobation rest on different grounds: election on the redeeming love of God that undertakes the salvation of the lost; reprobation on the moral necessity to manifest to the universe the nature and consequences of sin in moral personality.

3. Means are used of God to fulfil the purpose of election, but God uses no means to fulfil His purpose of reprobation. It is left to sin to run its course and receive its wages.

4. The fruits of election are attributable to divine grace, the fruits of reprobation to personal sin. This means that while there is grace to some, there is injustice to none.

5. While God finds pleasure in the salvation of the elect, He has sworn by Himself that He has no pleasure in the death of the wicked. God does not need sin or its retribution for His self-manifestation, but its reality in the universe can serve that end.

6. That the elect will constitute a recreation of the race under a new Head is evident, while the retribute are but the branches cut off from the tree of humanity. Christ will be revealed as the Saviour of the world, though many are lost in the process.