Offers of paradise are merely us as we are dwelling in perfect conditions; but in real Heaven it is us as we have become, dwelling in perfect conditions: the gap between us as we are and us as we have become is called theosis - it is the process through which men become more like God.
Heaven lies on the other side of theosis.
Theosis is the process by which Man becomes like God - God-like - specifically a Son of God. It is an essential but often neglected aspect of Christianity - essential in that it seems to be one way of describing our purpose in mortal life.
An account of the nature, operation and scope of theosis - an understandable account of how Man becomes like God - is (or ought to be) near the heart of Christianity.
Because without theosis, Heaven does not make sense; and if Heaven does not make sense then the necessary virtue of Hope is rendered incomprehensible.
So: here we go...
Theosis can be conceptualized in various ways - but I think they can be boiled down to two:
1. Man can become like God because Man starts out with a divine potential or essence. In other words, Man shares some kind of divine nature with God, a seed of divinity within (as it were) - and theosis is a process of growth: a process of growing this tiny divine potential.
2. Man can become like God by God's action - because God is omnipotent and can transform anything into anything else. God and Man are utterly different in nature, in kind - but Jesus Christ was both in a way that is incomprehensible, and we may become both in ways that are ultimately incomprehensible.
One of the problems for theosis is that many Christian traditions see salvation as the main thing to such an extent that being saved (from death, from Hell) becomes almost the whole thing. This makes sense when damnation is regarded as the default for mortal men. The saving of souls by evangelism, mission work, conversion is then the main activity of Christian churches.
Salvation is qualitative (yes-no) while Theosis is quantitative (how much?).
Theosis can only become a focus when there is a sense that either salvation has been-achieved already, or else when theosis is considered to contribute to salvation, contribute to that bimodal outcome - but this is not really theosis, but rather a path to salvation.
At any rate, and whatever the theological justification, a real-life church focus in the practice of theosis is seen when there is a background of solid faith in salvation: the theosis of monasticism in the the Catholic ages of faith, the focus on sanctification among puritans of the 17th century (with their assurance of salvation), and now spiritual progression among Mormons (for whom salvation, of varying degrees, is the default state and happens unless will-fully rejected).
I have had some difficulty in finding a metaphor to help me understand theosis - for instance I got stuck on the idea of theosis as an evolutionary process, which didn't seem to help at all. But I think I may have found a useful metaphor in terms of (a real) education.
Theosis is like education, especially when education is considered in its fullest and truest form when education is a about attaining performance of a complex role - attaining mastery: for example the education of a real musician such as a symphony conductor (called a Maestro - master), or a traditional doctor.
Such an education uses multiple methods to attain the goal of autonomous mastery: Experience, organized practice of tasks, repetitive drills, overcoming opposition (solving 'problems given by the Master), observation of Masters at work, formal teaching of facts and principles, multiple tests and evaluations with a final examination by performance of the real job and/or production of a Master-piece...
Without wanting to be too explicit, I think that there are potentially helpful analogies between the various processes of education, and what could be inferred to be theosis; if mortal life is considered as overall having been structured by God as a potentially educational process.
And just like education there must be educable potential and will to be educated in the apprentice, and educative elements (formally structured and informally personal) in the environment; and both sides are required.
When theosis happens, and how prolonged may be the period (restricted to mortal life, or going beyond mortal life?) varies between Christian traditions; as does the potential degree of theosis (i.e. different interpretations of the meaning and implications of Son-ship in the promise that Christians may become Sons of God - just how God-like may Men become?)
Still, such differences of detailed explanation aside, theosis broadly understood could be seen as the purpose of mortal life for those who have confidence in their own salvation; and its mechanisms could perhaps be understood by analogy with education.