William Wildblood has done an important post at his Meeting the Masters blog; which he gives the provocative title The World Is Perfect.
This truth flies in the face of common modern morality to such as extent that probably most people would regard it as actively-evil, insane or seriously-dumb even to consider the validity of the idea that my life and your life, and the lives of everybody who ever has been - has been the life we most needed (although almost never is it the life we ought-to lead, since people apparently very seldom learn from their experiences).
1. The first step is to recognise that this mortal life, the life between biological conception and death, is on the one hand extremely-important; and also on the other hand not the only life - and especially not the end of our lives.
We have an eternity to live after mortality; therefore much of what happens during this mortal life can be understood and made sense of only in that context.
2. As Christians; we know that God was the creator, and that we live in the midst of his creation; also that God is our loving Father and designed creation for our (ultimate, eternal) benefit.
For modern people, this entails that we reject the almost ubiquitous (and incoherent) idea that this world is some mixture of rigidly-determined and random; that each thing is just an effect of some previous cause - without end or beginning; or else things happens unpredictably and for no reason.
By contrast, we need to assume that everything happens for a reason and by some intent or another.
This means that the world is, ultimately, alive and conscious and therefore intentional - there are ultimate reasons for everything (although, naturally, we don't personally know the reason for more than a minuscule number of these happenings - but that they do have a reason, we do know).
3. Another closely-related modern confusion that we need consciously to reject is that there is no such thing as 'free will'.
A better world for free will is agency in the old sense of the word; or autonomy... meaning simply that an autonomous entity is one from-which intentions, motivations, thoughts can arise (without being-caused).
That is, a free entity is one which is (to some extent) its own cause, or a source of causes.
That is just what-agency-is.
(It is a metaphysical assumption that there are such entities. It is not something to be proved - and neither can it be proved. Determinism of everything, and the possibility of randomness are equally metaphysical assumptions - and indeed they are very recent metaphysical assumptions, held by only a small minority of modern people. The possibility of coexistant determinism and randomness is also a meatphysical assumptino - and one which is incoherent. Another common but incoherent assumption, for example in physics, is that something may occur randomly and yet also be statistically predictable.)
There are many agent entities in this world (for example people, but others as well) - and there is also God.
This means that this actual world we experience is on the one hand God's on-going creation and it is also the outcomes of multiple autonomous entities.
4. For a Christian, God has a destiny - a hoped-for development - for each one of us, as individuals.
God does not want every human to be the same ('clones'); but like any good parent, God rejoices in the differences between his children, and loves to see each (beloved) child develop uniquely and in-line with his own nature, abilities and aspirations.
At the same time, God's creation is bound together by love - and the unique development of each individual must cohere with that of each other in a heavenly harmony.
The first commandment is love God and the second to love our 'neighbours' - and these are the prime commandments - thus it is love, and only love, which enables creation to be Good.
5. This is the world which we each inhabit, as mortals.
God is always present and active in his creation - but mostly 'behind the scenes' - because it is a major part of the divine plan that we each develop our own uniqueness in our own way: actively not passively - by free choice and not by compulsion.
By 'behind the scenes' I mean that God ensures that the experiences we most need for our development will come our way. This is not something we need concern ourselves about - our proper concern is to experience these experiences fully (and not, for example - a common modern response - to avoid thinking about them) and to learn from them.
Each of us has different learning priorities; plus some people learn fast, while others do not learn at all. Others draw the opposite conclusions from their experiences than God intends... all of this is a necessary and intrinsic part of the free will/ agency/ autonomy of people.
So, often we need multiple repetitions before we learn that which we (personally) most need to learn), often we need extremely harsh experiences before we learn. (This is a matter of common observation and experience.)
And at the end of the day (as Jesus stated clearly) there were and are people who simply will not learn, who will neither listen to nor hear The Word. They can be given all sorts of experiences - they are shown miracles, shown love, hear or see divine communications - yet they will not learn.
This is because people really are autonomous agents. That is what people are. Necessarily. For better And for worse.
(And for worse, perhaps more frequently than for better...)
6. There are many and vital inferences to be drawn form the previous five points; but one that requires specific emphasis is that we must personally and in our own lives (as Christians) believe that this is indeed the best of possible worlds.
This is just not 'an option' - it is mandatory.
Actually understanding this is somewhat difficult, given the number of lies and errors that surround us, and the modern disinclination to think. And having understood it - it is difficult to live-by that understanding. Indeed, this is precisely one of the lessons we must learn!
So we must know this for ourselves, and for our own life. And we can expect that God will ensure that we have all the understanding we need for this purpose.
But we must Not try (and - always - fail) to explain why every detail of God''s creation is the best possible experience for every single one of the people alive now and throughout human history!
How could we possibly know this; and why would we need to?
So when someone comes-up with a (real or imagined, factual or garbled) description of some innocent or good person who either seems to have suffered very badly during mortal life - or some evil person who apparently had a gratifying (healthy, high status, powerful, cheerful...) mortal life... And when such 'examples' are put forward as contradicting the assertion tha this is the best possible world... We should never allow ourselves to be drawn-into trying to explain how exactly this example fitted into God's plan for creation!
(What was ridiculous about Dr Pangloss in Voltaire's Candide was not his assertion that this was the best of possible worlds; but his ludicrous and arrogant attempts to explain the precise reason for why every possible disaster to every individual actually contributed to the greater-ultimate-good, often in this mortal world. As if Pangloss personally knew the entirety of God's intent and creation's-causal web!)
We do not know all persons destinies, we do not know their inner minds and how they were actually gratified or suffered, we do not know what happens after a person dies...
In sum, we personally cannot link the events of someone else's mortal life with their individual destiny (and what that person most needed to know, or whether they indeed learned it); nor with the lives of all other people (whom God equally loves, as his children - albeit we are wicked children, he still loves us and want the best for every one of us); nor with the other entities of God's creation; nor can we understand how a person's mortal life was linked with their post-mortal eternal and resurrected life.
We cannot do such things, and if we try to do so - and to persuade another person of our rightness - then we only reveal our ignorance and makes ourselves ridiculous.
On the other hand, it is perfectly reasonable and to-be-expected that we can know a great deal of this kind of thing about ourselves; insofar as such knowledge is helpful to the main purposes of our mortal life - much of which is about learning to be active agents.
So it is quite likely that God wishes us to work-out such things for ourselves (rather than simply 'telling us') - partly because that is the basis mode of mortal life, and partly because that is the only way that many people can actually learn.
It is a commonly observed fact that many people can only learn many important things the hard way.
And when these 'things' that need to be learned are extremely important (for eternity), then that means that 'the hard way' is precisely the way that many such things will, of necessity, actually be learned.