Can you please cite a Church docuмent explaining how grace is lost without sin?

John 16:8-9 And when he is come, he will convict the world of sin, and of justice, and of judgment.  9 Of sin: because they believed not in me. 

What is it you don't get about it being a sin to not believe in Christ?

Can you please cite a Church docuмent explaining how grace is lost without sin?

Explain how the atheist above can be saved.  You've dodged that question multiple times now.

Theologians are unanimous that for adults there can be no supernatural faith without explicit belief in at least the Rewarder God, with most holding that explicit faith in the Holy Trinity and Incarnation, are absolutely necessary by necessity of means in order to have supernatural faith.

Adults are required to have the proper dispositions for Baptism in order for the Sacrament to confer supernatural faith and charity.  Period.  In an infant, however, these infused supernatural virtues are latent until such as time as the individual reaches the age of reason, at which time he too is required to have the necessary dispositions for Baptism.

Probably the same thing I don’t get about how I can lose grace by committing a mortal without the requisite full knowledge.

Can you please cite Church teaching explaining it to me?

The Scripture is itself the teaching. You don't believe in Christ, you sin - period. And remember, Christ and the Church are one. This is the dogma EENS.
There are many but here is one more...
Eph.5:6 Let no man deceive you with vain words. For because of these things cometh the anger of God upon the children of unbelief.  7 Be ye not therefore partakers with them.  8 For you were heretofore darkness, but now light in the Lord. Walk then as children of the light.

In their unbelief St. Paul says "your were darkness" - dark with sin - until they believe in Him. If you read into this because they did not know Christ that they were without sin then those are the vain words St. Paul is talking about.

The Catholic Dogma by Rev. Michael Müller, C.SS.R

CHAPTER V., Part II.


http://traditionalcatholic.net/Tradition/Information/The_Catholic_Dogma/Chapter-V_Part-II.html#PART%20II



Hence St. Thomas, speaking of faith, says: “The virtue of faith consists principally in submitting our intellect and will, with the help of God's grace, to the divine authority of the true Church charged by Jesus Christ to teach us what we must believe. He who does not follow this rule of faith, has no true faith at all." The reason of this is given above by St. Alphonsus; for how could we, without the Church, know that God has revealed anything at all? How could we know what he has revealed? How could we know the meaning of his revelations? How could we know the written Word of God? How could we know the meaning of Holy Scripture? For Holy Scripture does not consist in the words, but in the sense of the words. How could we know the extent of the divine revelations? For the extent of the divine revelations is greater than that of Holy Scripture. So, without the divine authority of the Roman Catholic Church, we can hold no revealed truth on divine authority; if we hold any Catholic truths, we believe them only on human authority; and such belief is no divine faith. Acts of divine faith, therefore, consist in believing firmly what God tells us through the divine authority of his Church. All heretics, formal as well as material, are separated from this divine authority, and therefore even the acts of faith made by material heretics are by no means acts of divine faith, in spite of their inculpable ignorance of the divine authority of the Church. Suppose such a Protestant has counterfeit money in his possession, which he innocently believes to be quite genuine, is his money, from being counterfeit, changed into genuine money by his inculpable ignorance in the matter. In like manner, the acts of faith made by a material heretic are counterfeit acts of faith, because they are not based upon the authority of God, speaking through the authority of his true Church. These acts are without a divine foundation.

In inculpable ignorance of this fundamental truth for true acts of faith there is no power whatever to change counterfeit acts of faith into divine acts of faith. All that can be said in favor of this kind of heretics is that they may have the disposition for believing what is right, and this disposition comes from God and prepares such Protestants for receiving the gift of the true faith when they come to know it.

Now let us suppose to be true what is impossible to be true, namely, that the act of faith made by a material heretic is a divine act of faith, as the Rev. A. Young asserts, it is very wrong for him to say that such an act of faith, as described by him, is, according to St. Thomas, meritorious, which means, deserving of an eternal reward in heaven. St. Thomas never said anything of the kind; he says that an act of faith is meritorious only when it proceeds from, and is united with, divine charity.—All good works, that are performed by a person without being in the state of true divine charity, are dead works.—If the Rev. Young gives the definition of faith given by St. Thomas, why has he not given us St. Thomas's explanation of his definition of faith?—A few lines after, St. Thomas says: “Charitate superveniente actus fidei fit meritorius per charitatem." When divine charity becomes joined to faith, the act of faith becomes meritorious. When St. Thomas gives the above definition of an act of faith, he speaks of a person who believes God, who speaks to him by his Church, as is evident from other passages in which he speaks of the faith of heretics. As long, then, as a material heretic, though through inculpable ignorance, adheres to an heretical sect, he is separated from Christ, because he is separated from his Body—the Catholic Church. In that state he cannot make any supernatural acts of divine faith, hope, and charity, which are necessary to obtain life everlasting, and therefore, if he dies in that state, he is pronounced infallibly lost by St. Augustine, St. Alphonsus and all the great Doctors of the Church.

But, says the Rev. A. Young: “I was baptized in infancy by a minister of the Protestant Episcopalian Church. I then received, as all baptized persons do, whether adults or infants, the infused virtues of divine faith, hope, and charity, with sanctify grace, and was made capable, by the grace of God thus given, to make distinct meritorious acts of divine faith, hope, and charity."

One of the effects of Baptism is that, when children are validly baptized, they receive, together with the indelible character of a Christian, the habit of faith,—or a capacity, a power or faculty which enables them, when they come to the use of reason, and are instructed by the Catholic Church in revealed truths, to make acts of divine faith, this habit of faith enabling them to see clearly and believe firmly the truths of the Catholic religion. A baptized child is a child of God, and God lives in the soul of that child and is its Father. So, when God speaks through his Church to that child, it easily recognizes the voice that speaks to him as the voice of God, and firmly believes whatever that voice teaches him to believe. But this habitual divine faith is lost by the profession of heresy, material heresy not excepted. To a child that is brought up in heresy, God does not speak when it hears the voice of a heretical teacher; if it believes that teacher, it believes not God, but man, and its faith is human, which cannot lead it to God. (See St. Thomas, De Fide, Q. V., art. iii.; Cursus Compl. Theologae, vol. 21, Q. III., art. iii., de Suscipientibus Baptismum. Instruction in Christ, Doct. chapt. ii.)

This may be more clear from the following: If a person who has come to the use of reason and professes heresy at the time of his baptism, he is indeed indelibly marked as a Christian, but he is not sanctified—the other supernatural effects of baptism being suspended for want of the proper dispositions or preparations which are required to receive not only the sacrament, but also its supernatural effects. One of the most essential requisites to receive these effects is to have the true faith, i.e., to believe God, speaking through the Catholic Church. Now heresy, material heresy not excepted, is a want of this faith, on account of which the supernatural effects of baptism are suspended. God cannot unite himself with a soul that lives in heresy, even though it be only material heresy. As the supernatural sanctifying effects in this case are suspended, so they are for the same reason, destroyed in him who was baptized in his infancy and became a heretic, though only a material heretic, when he came to the use of reason. This person, to be again reconciled with God, must renounce heresy, believe the Catholic Church, and receive worthily the sacrament of penance; or if this cannot be had, he must have perfect contrition or charity with the desire (at least implicit) to receive the sacrament of penance. The other person, however, will be reconciled with God and truly sanctified, as soon as he renounces heresy, believes the Catholic Church, and has at least attrition (imperfect supernatural sorrow) for his sins, because it is then that the supernatural sanctifying effects of baptism take place. It is therefore evident that, if these persons and others like them were to die in heresy, they would be lost forever. (See Theolog. Curs. Compl. De Confirmatione, Part II., Q. II., art. vi.)

"The Church,” says Dr. O. A. Brownson, "teaches that the infant validly baptized, by whomsoever the baptism be administered, receives in the sacrament the infused habit of faith and sanctity, and that this habit (habitus) suffices for salvation till the child comes to the use of reason. Hence all baptized infants dying in infancy are saved.

"But when arrived at the use of reason, the child needs something beyond this infused habit, and it is bound to elicit the act of faith. The habit is not actual faith, and is only a supernatural facility infused by grace, of eliciting the actual virtue of faith. The habit of sanctity is lost by mortal sin, but the habit of faith, we are told, is lost by a positive act of infidelity or heresy. This is not strictly true; for the habit may be lost by the omission to elicit the act of faith, which neither is nor can be elicited out of the Catholic Church; for out of her the credible object, which is Deus revelans et Ecclesia proponens, (God revealing and the Church proposing for our belief) is wanting. Consequently, outside of the Church there can be no salvation for any one, even though baptized, who has come to the use of reason. The habit given in Baptism then ceases to suffice, and the obligation to elicit the act begins.

“We may be told that it may not be through one's own fault that he omits to elicit the act, especially when born and brought up in a community hostile, or alien to the Church. Who denies it? But from that it does not follow either that the habit is not lost by the omission, or that the elicitation of the act is not necessary, in the case of every adult, to salvation. Invincible ignorance excuses from sin, we admit, in that whereof one is invincibly ignorant, but it confers no virtue, and is purely negative. It excuses from sin, if you will, the omission to elicit the act, but it cannot supply the defect caused by the omission. Something more than to be excused from the sin of infidelity or heresy is necessary to salvation."

But, continues the Rev. A. Young, “as I was a baptized Christian, I did not, neither could I, lose the capacity to make meritorious acts of divine faith, no matter whether I made them or not; no matter what I believed or disbelieved as I grew up; no matter whether I became a Protestant, Jєω, Mahomedan, or infidel. I will be a baptized Christian for all eternity, because the indelible mark of baptism cannot be taken out of my soul. In this case I was capable of making meritorious acts of divine faith."

What stupid and most absurd assertion this! Is it possible that a priest can be so ignorant as to assert what no well­ instructed Catholic child would assert! Only he who lives in the true faith and in true charity with God has the capacity of making meritorious acts of divine faith. And yet the Rev. A. Young, in his unpardonable ignorance, solemnly asserts that a baptized Protestant, or a baptized Jєω, or a baptized Mahomedan, or a baptized infidel is as such capable of making meritorious acts of divine faith, because he bears in his soul the indelible mark of baptism. Who ever taught and believed such nonsense! How can a priest be so ignorant as to confound the indelible character of baptism with the supernatural graces of this sacrament, which are lost by the profession of heresy and infidelity!

“Again," continues the Rev. A. Young, "God gives his grace to all persons; that is, he moves their will, as St. Thomas says in his definition, to compel the intellect to give assent to divine truth. Therefore God moved my will to that end."

To understand how necessary the grace of God is to believe the true religion, we quote the following from St. Thomas: The final beatitude of man, says St. Thomas, consists in the beatific vision of God. As this end of man is far above the strength of human nature, it was necessary that God should teach him how to obtain everlasting beatitude. So God has revealed certain supernatural truths, which are above the human understanding, to lead him to the beatitude of heaven. To acquire the knowledge of these truths, he must learn them from God, through those to whom God has communicated them and whom he has commissioned to teach them infallibly, in his name. Then it is necessary that he who learns these truths from God through his infallible teacher, should give his firm assent to them. The cause which induces man to give his assent to these supernatural truths may be twofold: it may be exterior, such as a miracle which a person sees, or some one who tries by his words to persuade a person to believe. Neither of these two causes is sufficient to create faith; for of those who see one and the same miracle, and of those who hear the same sermon on faith, there are some who believe and others do not believe. Hence it is necessary to assign another interior cause which induces a person to assent to the truths of faith. The Pelagians (heretics) taught that the free-will of man is this interior cause which induces him to believe, and that on this account the beginning of faith, is of man himself, in as much as he is ready to believe divine truths, but that the perfection of faith is from God, who proposes the truths which must be believed. But this is false, for by giving his assent to the truths of faith man is raised above his natural condition, and therefore the cause that raises man above his natural state must be supernatural, moving man interiorly to believe, and this interior supernatural cause is God. Hence the assent to the truths of faith, which is the principal act of faith, must be attributed to God who, by his grace, interiorly moves man to believe the truths of faith. Although the act of believing consists in the will, yet it is necessary that the will of man, should be prepared by the grace of God, in order to be raised to those things witch are above human nature.” (22. q. ii., art. and q. vi., art. 1.) It is, therefore, necessary that God should enlighten the intellect and move the will of man to believe the true religion when it is preached to him; but it would be blasphemous to say that God moves the will of man to believe heretical doctrine. And yet the Rev. A. Young asserts “that God moved his will to give his assent to divine truth” in Protestantism. And what he believed of the true divine teacher of God—the Roman Catholic Church, he candidly tells us when he says:—

“I was brought up to believe that the Roman Catholic Church was the Church of Antichrist; that she was the scarlet woman of Babylon, and the Pope the man of sin; that she taught false doctrines; that she was the great enemy of all the Christian truth, morality, and love of God. I read the wandering Jєω, I also read many other horrible, lying, immoral books written to defame the Roman Catholic Church; and as there was no opportunity for me to learn better I believed them to be true."

Now, who will be foolish enough to believe that God moved the will of Rev. A. Young to believe such devilish doctrines? God enlightened his intellect and moved his will when he detested those doctrines and made his profession of faith in the only true Holy Catholic Church; God moves the will towards what is good, but not towards what is bad; he cannot be the author of evil.

I've cited that it's unanimous teaching that supernatural faith is impossible without explicit faith.

This is going on half a dozen times now where you've dodged the question about the the individual who is an atheist at the time he reaches the age of reason.

So the two Church teachings from which my conclusions follow:
1) adults are required to have the proper dispositions for the Sacrament of Baptism in order for the Sacrament to be able to justify them
2) those who lack explicit faith in at least a Rewarder God cannot have supernatural faith

My conclusions flow directly from these two Church teachings.  You have yet to address either of these, but keep obsessing in OCD fashion about how normally for adults they have to commit a mortal sin to lose sanctifying grace.

Neither you, nor anyone else, has explained how, according to the Church, grace can be expelled from a soul without grave sin (or conversely, how those in the state of grace can be damned).

I’ll bow out of the thread until someone can do that, as the failure to do so is a glaring “concedo.”

The habit of sanctity is lost by mortal sin, but the habit of faith, we are told, is lost by a positive act of infidelity or heresy. This is not strictly true; for the habit may be lost by the omission to elicit the act of faith, which neither is nor can be elicited out of the Catholic Church; for out of her the credible object, which is Deus revelans et Ecclesia proponens, (God revealing and the Church proposing for our belief) is wanting. Consequently, outside of the Church there can be no salvation for any one, even though baptized, who has come to the use of reason. The habit given in Baptism then ceases to suffice, and the obligation to elicit the act begins.

Thanks for finding a source.  THIS ^^^ is what I've been saying the entire time.  It requires understanding the definition of a virtue or a habit, and understanding how this habit is merely infused in someone without the use of reason, but for those with reason it requires an active act of faith.

Neither you, nor anyone else, has explained how, according to the Church, grace can be expelled from a soul without grave sin (or conversely, how those in the state of grace can be damned).

I’ll bow out of the thread until someone can do that, as the failure to do so is a glaring “concedo.”

Ah, so you're going to pick up your toys and leave.  Typical.  What a baby.  Father Mueller explains it in the citation provided by trad123.  You don't understand the nature / definition of a virtue or habit and how the infused supernatural virtue received at Baptism requires active cooperation from someone who has reached the use of reason.

You absolutely refuse to answer the question about how a baptized infant who reaches the age of reason as an atheist can be saved when the Church teaches that for adults explicit faith is required for supernatural faith (and therefore supernatural charity).  So instead you stomp away.  Your failure to answer this question is the "concedo".

You spent how long at the seminary and you don't understand what virtues and habits are and what their relationship to act is?