If God were all-powerful, all-knowing and all-good, wouldn't that be self-evident?

Generally one has to combine omnipotence with omnibenevolence for natural disasters and suffering to create a theological conundrum. The question is (medieval metaphysical logic aside) why does god have to be omnipotent or omnibenevolent (human anthropomorphic wishful thinking aside)?
God (if one exists at all) may have entirely different goals (like creativity, experience and novelty) and different methods of achieving those goals like natural process and physical law.
Try the title of Charles Hartshorne's small treatise "Omnipotence and other Theological Mistakes"

Based on what reasoning should we conclude that the presence of those things is evidence that God (if he exists) is not benevolent? — baker

Epicurus’s old questions are yet unanswered. Is he willing to prevent evil, but not able? then is he impotent. Is he able, but not willing? then is he malevolent. Is he both able and willing? whence then is evil? — Hume

It is true that one could argue, like Leibniz, that it was logically impossible for God to have created the best possible world without the evil it contains, because some greater goods logically depend upon certain evils in order to exist. In this respect however, I agree with Russell's assessment:

Leibniz's solution of the problem of evil, like most of his other popular doctrines, is logically possible, but not very convincing. A Manichean might retort that this is the worst of all possible worlds, in which the good things that exist serve only to heighten the evils. The world, he might say, was created by a wicked demiurge, who allowed free will, which is good, in order to make sure of sin, which is bad, and of which the evil outweighs the good of free will. The demiurge, he might continue, created some virtuous men, in order that they might be punished by the wicked;
for the punishment of the virtuous is so great an evil that it makes the world worse than if no good men existed. I am not advocating this opinion, which I consider fantastic; I am only saying that it is no more fantastic than Leibniz's theory.

Based on what reasoning should we conclude that the presence of those things is evidence that God (if he exists) is not benevolent? — baker

The way I see it, if God exists and is omnipotent, then I think he can do as he pleases. He is under no obligation to submit his actions or the motives of his actions to human scrutiny and judgment.

Otherwise, he would become subordinate to the human mind which is absurd. Either he is God or he isn't.

Based on what reasoning should we conclude that the presence of those things is evidence that God (if he exists) is not benevolent? — baker

Hmm. Key words: reasoning, presence, evidence, exists, benevolent.

I am sure that any answer will depend on (the) understanding of these words, both as to substance and quality of the understanding.

Let's start with reasoning. What exactly is that, and what exactly does it mean to "conclude" anything from reasoning? And what would that have to do with god?

The way I see it, if God exists and is omnipotent, then I think he can do as he pleases. He is under no obligation to submit his actions or the motives of his actions to human scrutiny and judgment. — Apollodorus

That is not the question. The questioning presupposes goodwill. Then the existence of suffering is illogical.

If God is not benevolent, then it is a different question.

That is not the question. The questioning presupposes goodwill. Then the existence of suffering is illogical.

If God is not benevolent, then it is a different question. — SolarWind

If you ask the wrong question you will inevitably get the wrong answer.
Other than wishful thinking and human anthropomorphism there is absolutely no reason to assume god is omnibenevolent or for that matter omnipotent.
Given the assumption of both omni's (all Christian apologetics and other theological hand waving aside) there is no convincing or satisfactory response to the religious "problem of evil". Thus it becomes a major problem for religion and a major source of disbelief in any form of deity, sacred, holy or numinous entity. That paves the way for a souless universe devoid of any inherent value or purpose. IMHO bad philosophy and bad religion combined.

If you ask the wrong question you will inevitably get the wrong answer. — prothero

I'm not the thread opener and I'm just making case distinctions.

That paves the way for a souless universe devoid of any inherent value or purpose.

Why can't there be a universe WITH souls and WITHOUT gods?

Based on what reasoning should we conclude that the presence of those things is evidence that God (if he exists) is not benevolent? — baker

With form (creation) comes opposites:

up down

left right

good bad

That is not the question. The questioning presupposes goodwill. — SolarWind

You could be right. However, the question is not about any goodwill but about God's goodwill.

And the main attribute of God seems to be that he is omnipotent or powerful:

God is usually conceived of as being omnipotent, omniscient, omnipresent and omnibenevolent as well as having an eternal and necessary existence.

God – Wikipedia

Conceptions of maximal greatness differ but theists believe that a maximally great reality must be a maximally great person or God. Theists largely agree that a maximally great person would be omnipresent, omnipotent, omniscient, and all good.

Concepts of God – SEP

God a. A superhuman person regarded as having power over nature and human fortunes

– Oxford English Dictionary

And the main attribute of God seems to be that he is omnipotent or powerful:

God is usually conceived of as being omnipotent, omniscient, omnipresent and omnibenevolent as well as having an eternal and necessary existence. — Apollodorus

Being that this is a philosophy forum maybe we should try a little philosophical theism and dispense with preconditions or presumptions which cause us profound cognitive dissonance regarding science and experience. Religious discussion on the forum is too often just a repetition of medieval scholastic theology as though the advances of science could or should have no influence on our religious views.
Man is no longer the crown of creation and the earth is no longer the center of the universe, other views of deity seems necessary for the modern time.

From Wikipedia
Philosophical theism is the belief that the Supreme Being exists (or must exist) independent of the teaching or revelation of any particular religion.[1] It represents belief in God entirely without doctrine, except for that which can be discerned by reason and the contemplation of natural laws.

Philosophical theism conceives of nature as the result of purposive activity and so as an intelligible system open to human understanding, although possibly never completely understandable. It implies the belief that nature is ordered according to some sort of consistent plan and manifests a single purpose or intention, however incomprehensible or inexplicable. However, philosophical theists do not endorse or adhere to the theology or doctrines of any organized religion or church.

Being that this is a philosophy forum maybe we should try a little philosophical theism and dispense with preconditions or presumptions which cause us profound cognitive dissonance regarding science and experience. — prothero

It may well be a philosophy forum but we still use words in the sense they are normally understood - unless otherwise stated.

Plus, by defining God as "benevolent" the OP seems to be using conventional terminology.

If God has to allow pain for a greater good, there is still the problem of predestination. Why create people who will go to hell or not ensure that they go to heaven?

The only reasonable conclusion is that there is no god.

The only reasonable conclusion is that there is no god. — Banno

If our only choices are God as defined above and your conclusion, I have to agree. It just seems traditional theism and atheism should not be the only possibilities in the philosophy of religion section.

What doesn't exist is the unintelligible god described by the theologians, the one common to Abrahamic religions. There's still room to feel awe.

Based on what reasoning should we conclude that the presence of those things is evidence that God (if he exists) is not benevolent? — baker

Depends on which 'benevolent' God you are talking about.

If we consider the Christian God:

...not a single sparrow can fall to the ground without your Father knowing it. And the very hairs on your head are all numbered. So don’t be afraid; you are more valuable to God than a whole flock of sparrows.” (Matthew 10:29-31)

It would seem to be the opposite of benevolence for God to know about natural disasters and starvation and cancer and suffering and let it go unchecked when suffering can be relieved. If humans are valuable to it then this appears to demonstrate a callous disregard. Is it possible for a non-interventionist god to be benevolent?

I am certain any competent theological sophist can make a virtue out of all this.

By the way, I know believers who say that God helps them to get jobs and find parking spaces. That's great. Pity God's inactive on infant leukemia.

A common line of reasoning against God's presumed omnibenevolence goes like this:

If God was omnibenevolent, there wouldn’t be ... any earthquakes, tsunamis, droughts, floods, wars, children with genetic dysfunctions, ... and in general, there wouldn't be any suffering.

But why should the absence of these things be evidence of God's benevolence?

Based on what reasoning should we conclude that the presence of those things is evidence that God (if he exists) is not benevolent? — baker

If there be a perfect being which infinite power and infinite goodness, then we'd expect to see some effects from that -- that the being would use their power to do good things, for instance.

Perhaps we could take the claim down a notch from your beginning, and just leave it at that.

There is so much evil and suffering in the world that it becomes hard to believe in an all-powerful loving God. Not this or that specific evil, but the overwhelming amount of suffering which has nothing to do with moral worth or goodness.

I think God has delegated some of his benevolence to his prized creation … mankind …through scientific progress we have cured many things and will eventually end all biological suffering without impacting our free will. We sure have the mental capacity just more breakthroughs in the scientific fields are required. As for other evils that exist such as man killing man well again that is free will just because we’re imperfect does not mean God is.

I think that the problem of natural evil posits that God can not be omniscient, all-powerful, and omnibenevolent simultaneously. If God is merely omnibenevolent, then, he doesn't have to prevent global catastrophes, as he may neither know of them nor be capable of doing so. If God is all of those things simultaneously, then it doesn't make any sense for them to happen.

It goes a bit further in begging the question as to what good a god is who does not possess all of those qualities simultaneously. If a god is omniscient and all-powerful, but not omnibenevolent, then it could be evil. If a god is only all-powerful and omnibenevolent, then it wouldn't know what to put into effect. If a god is omnibenevolent and omniscient, then, what can it do?

It pretty much holds up to this very day. Epicurus was a genius. He even advocated for peace, the freedom from fear, and the absence of pain. Everything is good about Epicurus.

This doesn't address the evils that are not caused by man that are simply cruel suffering with no benefit.

We don't have to delve into the pit of nastiness. It's not hard to find examples.

If God has to allow pain for a greater good, there is still the problem of predestination. Why create people who will go to hell or not ensure that they go to heaven? — Gregory

If one is a massive badass -- excuse the language -- motherfucker, then one can do so.

We humans tend to judge God by our own standards, as different as they might be. So those people who have a humanist worldview tend to be appalled by the idea that God should be viewed as omnibenevolent _and_ omnipotent, given the massive suffering that so many people must endure already here and now (to say nothing of the prospect of eternal suffering). But people with a more Darwinist outlook might be better able to incorporate the way things usually are in this world with the idea that God is omnibenevolent _and_ omnipotent.

I believe that if God exists, he is a Trumpista. Seriously. It took me a long time to get to this point.

Pity God's inactive on infant leukemia. — Tom Storm

That's because the children must pay for the sins of their parents!

Other than wishful thinking and human anthropomorphism there is absolutely no reason to assume god is omnibenevolent or for that matter omnipotent.
Given the assumption of both omni's (all Christian apologetics and other theological hand waving aside) there is no convincing or satisfactory response to the religious "problem of evil". Thus it becomes a major problem for religion and a major source of disbelief in any form of deity, sacred, holy or numinous entity. — prothero

If we drop our humanist sensitivities, a whole new world of opens up, a world of new ways of conceiving goodness and justice. Capitalism has been teaching us that for a couple of centuries now, it's time we learned the lesson.

Think of God as a capitalist business owner. It's simply in his best interest to make the world run as he pleases, and he also has the power to make it happen.

It's actually strange that so many secular people have been conceiving of God in, basically, socialist terms; ie. that God should be a socialist, or he doesn't exist.

I think God has delegated some of his benevolence to his prized creation — Deus

Suppose he does this. Does he also delegate his responsibility for what people do?

If is actions - giving free will to humanity - result in evil, and he knows this, he remains culpable.

There would be few humanists who did not adhere to the notion that humans evolved. Seems you have this somewhat muddled.

AH, I see - so god is not at all moral. That might work.

The inexistence of nonviolent liberal communism globally is my refutation of the benevolence of God, at least, in so far that God is omnipresent, omnibenevolent, and all-powerful, but, I suppose that God could just merely be benevolent and incapable of either understanding or having any effect upon the world. I must admit that I do feel that way sometimes.

Not moral by humanist standards. But by Darwinist ones -- sure.

Humanism is the view that morality is found in what humans choose, and so is not found in divine commendation nor in evolutionary necessity.

Do you agree?

That is, the key ingredient in humanism is the capacity of people to become better.