No one's 100% certain what's going to happen when we die. We need only listen carefully to today's three readings to discover that our ancestors in the faith had differing ideas about this unavoidable event. As a biblically-formed people, we must be careful not to uncritically accept some catechism explanations about the afterlife, explanations based more on a desire to reconcile contradictory biblical theologies than on an honest attempt to explain the reasons behind those divinely inspired, different beliefs.
In my grade school catechism classes, for instance, I learned that "the gates of heaven were closed" because of Adam and Eve's sin. No one could get into heaven until Jesus died for our sins. Only later did I discover that teaching was based on the observation that, except in the late Wisdom writings, none of the Hebrew Scriptures' important people were ever spoken of as "going to heaven" after they died.
Scholars tell us the basic reason for the sacred authors' silence about heaven, as we know it, wasn't because they thought the gates of heaven were closed. Until those late Wisdom books were written - a century or so before Jesus' birth - they simply had no concept of heaven. As we know from the Wisdom readings employed in our funeral liturgies, once heavenly belief entered their theology, most Jews believed that those faithful to Yahweh in this world continued to live with Yahweh in heaven, even before Jesus' death and resurrection.
That means in the 6th century BCE, when Ezekiel's Yahweh speaks about opening graves and raising people from the dead, God's not referring to having certain individuals live forever in heaven. Yahweh is simply promising to return those Jews to Israel who died before being liberated from the Babylonian Exile. The understanding is that, after they live some years in the Holy land, they'll once again die.
It's important also to note that part of the reason behind our belief in a particular and a general judgment comes from differing opinions in the Christian Scriptures about what happens to Christians who die before Jesus' Second Coming.
In I Thessalonians - the earliest Christian writing we possess - it's clear Paul thought dead Christians would have to spend a short time in the grave until Jesus arrived and raised them up to a new life. We presume Mark and Matthew, who expected his Second Coming in their life-time, shared Paul's belief.
Things change with Luke. He takes for granted Jesus won't return until he and everyone in his community have died. He believes that, at the moment of death, Jesus' followers experience a "personal Parousia:" Jesus comes for them and immediately takes them into heaven with him. That's why his Jesus can assure the good thief, "This day you will be with me in paradise." If the good thief were in Mark and Matthew, their Jesus would have promised, "After a short time in the grave, you'll be with me in paradise." Luke's personal Parousia eventually develops into our particular judgment; Paul, Mark and Matthew's Second Coming becomes the general judgment, even though our sacred authors thought of them as either/or, not both/and.
But, as we hear in today's gospel pericope, John's Jesus goes one step further by assuring Martha, "I am the resurrection and the life; those who believe in me even if they die will live, and those who live and believe in me will never die." John's convinced that what we're looking for in the future we somehow already have right here and now. His Jesus would have told the good thief, "Once you believe in me, you're already in paradise."
Perhaps the best way to approach life after death is just to fall back on Paul's insight: "If the Spirit of the one who raised Jesus from the dead dwells in you, the one who raised Christ from the dead will give life to your mortal bodies also, through his Spirit dwelling in you." I suggest we let Jesus work out the details.