Ask them to name a country or a system that promotes a 50:50 system of justice between freedom and death where if you are found guilty of even the slightest crime (I hope we all do agree that there are different degrees of crime?) death is the only outcome and if you are found not guilty freedom is granted.
If they can you’ll probably find that it is in a country where there is a dictatorial regime. God is no dictator therefore this model would not be pleasing to Him.
If they can’t name one then ask them why they think God would have a justice system so different from the one operating in their midst.
Ask them to explain to you how the democratic justice system operates and why people get different sentences.
If you need a more theological outlook then see New Advent for the following:
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There are several passages in the New Testament that point to a process of purification after death. Thus, Jesus ChristSon of man, it shall be forgiven him: but he that shall speak against the Holy Ghost, it shall not be forgiven him, neither in this world, nor in the world to come." According to St. Isidore of Seville (Deord. creatur., c. xiv, n. 6) these words prove that in the next life “some sins wil be forgiven and purged away by a certain purifying fire.” St. Augustine also argues “that some sinners are not forgiven either in this world or in the next would not be truly said unless there were other [sinners] who, though not forgiven in this world, are forgiven in the world to come” (De Civ. Dei, XXI, xxiv). The same interpretation is given by
Gregory the Great (Dial., IV, xxxix); St. Bede (commentary on this text); St. Bernard (Sermo lxvi in Cantic., n. 11) and other eminent theological writers. declares (Matthew 12:32): "And whosoever shall speak a word against the **
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A further argument is supplied by St. Paul in I Cor., iii, 11-1,5: "For other foundation no man can lay, but that which is laid; which is Christ Jesus. Now if any man build upon this foundation, gold, silver, precious stones, wood, hay stubble: Every man’s work shall be manifest; for the day of the Lord shall declare it, because it shall be revealed in fire; and the fire shall try every man’s work, of what sort it is. If any man’s work abide, which he hath built thereupon, he shall receive a reward. If any man’s work burn, he shall suffer loss: but he himself shall be saved, yet so as by fire." While this passage presents considerable difficulty, it is regarded by many of the
Fathers and theologians; and he cites to this eftect: and theologians as evidence for the existence of an intermediate state in which the dross of lighter transgressions will be burnt away, and the soul thus purified will be saved.
of course you can use the “How to explain Purgatory to Protestants” at cin.org/users/james/files/how2purg.htm**