What is universalism and is it wrong? For example, in 1 Corinthians 15:22 does the all refer to everyone (or Romans 5:18)? Will everyone eventually be saved and make it into heaven?
Universalism is the view that at some point everyone will be saved. This may happen at the end of time, or else at some point in eternity, but no one is destined to perish in hell forever. There are internal debates and differences within universalism as to when exactly everyone is saved; some argue that there may be hell for some people for a time, but in the end, they too will be saved. The universalist case is that Jesus died for all people and so all people will live in Heaven forever. As a further point, universalists may argue that a God who is love cannot and will not send people or keep people in hell forever.
Not all universalists support their claims with reference to God’s word, but when they do, they may highlight texts like those mentioned in the question, texts that seem to say “all” will live.
Initially, we too may wonder about these texts, for at first read they may seem to favour a universalist view. Believing in universalism may be appealing, since if it is true, why be urgent and serious in seeking the Lord, in living ready for Jesus to return, in preaching the gospel, or in bearing witness to the nations? Everyone can relax. This highlights the problem with universalism. While it may appeal for support to some texts (which, in fact, it wrongly interprets), it ignores or dismisses many others, including, for example, all the texts that describe an ultimate divide between people, those who by God’s grace believe and are saved, and those who in their sin do not believe and are judged and condemned forever. Think of John 3:36, “He that believeth on the Son hath everlasting life; and he that believeth not the Son shall not see life; but the wrath of God abideth on him.”
Given the clarity of a text like that and many others, we should go back to passages like the ones mentioned in the question and see if they mean something other than what the universalists claim. Rereading 1 Corinthians 15:22 for instance, we notice how the word “all” at the end of the text is qualified by the words before it: “in Christ”. In other words, the point is that all who are in Christ, that is, all who believe in Him and belong to Him will live. With Romans 5:18, it’s the larger context that helps to make clear that the “all” who benefit from the righteousness of Christ are all who believe in Him (see Romans 5:1 for example).
In conclusion, a faithful reading of Scripture, many individual texts, and also the entire story line of the Bible, makes it clear that universalism is incorrect, and dangerous. “For God so loved the world, that he gave his only begotten Son, that whosoever believeth in him should not perish, but have everlasting life” (John 3:16; see also Lord’s Day 7 of the Heidelberg Catechism, Q&A 20).