I argued in the link below that justifying faith must be distinguished from cognizant-belief, but never separated in the lives of those capable of understanding. (A reading of that entry will help in understanding what follows.) If my thesis is false and belief in certain gospel propositions is necessary for justifying faith, then infants can be united to Christ by the Holy Spirit without having received pardon from God due to a want of belief in propositions. In other words, if the essence of justifying faith requires cognizant-belief, then infants cannot be forgiven in infancy, or justification is not always by grace through faith alone.
However, if we understand saving faith as a sovereign work of God whereby He subdues a person’s heart and renews the entire soul after Christ, then it is easy to see that elect infants can be justified by faith alone prior to comprehending the gospel. Accordingly, if a justified infant lives to years of maturity, he will in time believe to be true whatsoever is revealed in the Word… and in particular will accept and rest upon Christ alone for justification, sanctification, and eternal life…
What I find ironic in the contemporary Reformed landscape is that those who so strenuously argue that justifying faith is not “obedient” faith also argue that all men everywhere are commanded by God to repent and believe the gospel in order to appropriate Christ's righteousness. Now how does one willfully follow a command (i.e. savingly believe from beginning to end) without obeying the command? One can't. Therefore, belief can be obedient if it results from a command; so if faith is belief, then faith can be obeident-faith! Yet, if we acknowledge that justifying faith is a subdued heart that must exercise itself in belief when confronted with God’s word, then of course justifying faith cannot be “obedient” faith for a dead man (or infant) who comes forth from the grave – ready to believe — does not do so out of obedience, let alone understanding. The point is simply this. If justifying faith is belief, then of course it can be obedient faith because belief always engages the mind and what we believe can be in response to a command. However, if what I say is true, that justifying faith is the propensity to believe all of God's truth from a posture of being recreated, then it is "by this faith" one can believe in obedience; but faith itself is not obedient anymore than Adam was obedient by being created out of the dust of the earth or Lazarus was obedient by coming forth from the grave.
http://reformedapologist.blogspot.com/2006/04/is-faith-belief.html
http://reformedapologist.blogspot.com/2006/04/is-faith-belief.html