The fundamental difference between using AI to train images and a human using those same images for inspiration is originality. AI cannot add anything new or original to the work to make it transformative and it's own. Its just rehashing images and patterns in imitation. Humans when when using art for inspiration either add enough of their own creativity to their work to make it transformative or end up violating copyright sane as AI is doing
To be fair: to the untrained eye, that "inspiration" looks like random luck or chance, which has led to the notion that writers and painters are just throwing random ideas around until they stumble upon something nobody else has though of. It's where that whole "thousand monkeys with typewriters" analogy* comes from.
Apologies for the long, rambling post about art.
My first degree is an art degree (I'm an artist who learned engineering!), and at least once in every class there would be one student bashing Jackson Pollock or Clyfford Still for their painting style. "It's just random paint splatters! Anybody can do that, what makes them so special?!" And yes, to the untrained eye (and even to the partially-trained eyes of many art students) abstract paintings really do seem like random blobs of color, applied without technique or skill.
Well, computers can do random blobs of color! That means computers can do art! Right? That's how that works, right? There's no difference! Right? Guys, am I right? (No.)
It is called "expressionism" because it is expressive--when you look at a Jackson Pollock painting, you are looking at his emotion and intent. The paint, the patterns, the force and direction from which it was applied, the decisions he made, are all intended to be evocative of emotion, force, or movement. The way we learned it at university, the will of the artist is the "paint" and your mind is the "canvas." You look at the colors and shapes and your brain will reflexively look for patterns and images. They are applied in such a way as to suggest movement, maybe remind you of feelings or memories. You wonder what the artist was thinking. You imagine what the artist might be trying to say, what they might have been going through at that moment in their life.
Well, you can also look at an AI-generated image, and it can remind you of feelings or memories. But you don't wonder what it was thinking, because AI doesn't think. You don't wonder about the decisions it made, because it was just running an algorithm. You don't imagine what it's trying to say, because AI isn't saying anything. You don't wonder what the artist might have been going through, because it's a machine--it's not going through anything, and has neither moments nor life. Sure, you will see random blobs of color in the style of Famous Artist, and your brain will try to spot patterns and images, but that's the limit of the viewer's appreciation. And the only way to bypass this is to hide the use of AI, or trick/deceive the viewer into believing it was created by a human.
I'm using abstract expressionism as an example here, but it applies to all forms of creativity: painting, sculpture, writing, acting, dancing, all of it. When you remove the human connection, the work suffers. Sometimes greatly.
If you show me two similar images side-by-side, both painted by the same human in the same style, and then tell me "the one on the left was created by AI," my appreciation will be greatly diminished for the one on the left. (I don't know what this says about me or my training, but I doubt I'm the only one who feels this way.) Sure, I can still appreciate it for what it is, and say "yes, that's a picture of a bird sitting on an apple" but as soon as I suspect it was created by AI, I will no longer be able to think "hmm, that was a really creative decision to use an endangered lark perched on an apple with the supermarket price tag still attached, what a great juxtaposition of rampant consumerism with the current environmental crisis." The AI-generated image will never be more than just an image. A good image, sure, maybe even a realistic one--but only just an image.
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*this terrible analogy always bothered me. The monkeys would die of old age, the warehouses would all run out of paper, the typewriters would break and fall apart, the building they are in would decay, etc.,
long before even a single sonnet was accidentally created, let alone the entire works of Shakespeare. But sure, let's ignore that and every other practical limit of reality so that we can focus on a faulty argument about infinity. (eyeroll) I need to go lie down.