Thankyou @MemeFan for answering my seemingly pedantic questions. It's been very helpful:
Creationism is the belief that God actually created life as stated in scripture, creating all major kinds of creatures and setting the whole thing going. However, He created life with the ability to do everything we see it do today - including adapting to new circumstances in the ways that you discuss (e.g. a T-cell determining how to respond to a new threat). The fact that life is intelligent and adaptable is taken as evidence of intelligent design, not evidence against it - it is just further evidence of how amazing life is. No machine made by humans can heal itself and adapt in the way that life can, only something made by God can do that.
As you have said yourself, it is inconceivable that something so extraordinary could originate by chance. God has to be involved.
In a population of bacteria, there are always a small number that are resistant to antibiotics, through natural mutations. Usually, these mutations are actually harmful, so those bacteria do not thrive. For instance, bacteria will naturally encounter low levels of penicillin in the environment, and have a natural ability to produce the penicillinase enzyme to break it down. But a large dose of penicillin when used as a medicine will overwhelm the bacteria and kill them. A bacteria that has a mutation that causes it to over-produce penicillinase will be resistant to those high doses of penicillin - but in normal circumstances that bacteria would be wasting energy producing too much of this enzyme unnecessarily, so will be outcompeted by others. However, when subjected to penicillin as a medicine, all the other bacteria will die and only that one will survive. Its offspring are also resistant to penicillin, so when the population recovers it will be all penicillin resistant. But this is not the addition of a new ability, it is only natural selection. When the antibiotic is removed, any surviving non-resistant bacteria will outcompete the resistant ones, and the population will eventually return to its non-resistant state.
Likewise, if a chemotherapy treatment reduces the number of cancer cells to 1-2%, which cancer cells do you think survived the treatment? The ones which, for some reason or another, were already resistant to the treatment. Clearly they were already resistant, because if they were not they would also be dead just like the other 99%. When those breed up the whole population will have that characteristic. It doesn't mean they evolved a new ability in response to the chemotherapy. It just means that those that already had that feature were selected for.
We use this all the time in farming, as we have to deal with drench resistance in intestinal worms in livestock. If you drench all the animals repeatedly with the same drench (medicine to kill intestinal worms), the few worms that are naturally resistant will be the only ones that survive, and eventually all of the worms on your farm will be resistant and the drench will no longer work. However, if you leave some animals undrenched as "refugia" - places where worms that are not resistant can survive - the population will be continually re-seeded with these susceptible worms. As the susceptible worms are actually fitter in normal circumstances (the resistant ones weren't "better" or "more evolved"), they will outcompete the drench-resistant worms, and ensure that the drench continues to work.
I see the issue. You are defining all change as "evolution". Most creationists don't use that broad a definition. A creationist would use the term "evolution" to mean large-scale changes that, importantly, increase complexity or add wholly new structures. For instance, changing from a fish to an amphibian - this requires the addition of lungs and legs. Or changing from a bacterium to a horse - this greatly increases complexity. Smaller-scale changes would only be referred to as "adaptation". So to some extent we are talking at cross purposes.
Creationism is the belief that God actually created life as stated in scripture, creating all major kinds of creatures and setting the whole thing going. However, He created life with the ability to do everything we see it do today - including adapting to new circumstances in the ways that you discuss (e.g. a T-cell determining how to respond to a new threat). The fact that life is intelligent and adaptable is taken as evidence of intelligent design, not evidence against it - it is just further evidence of how amazing life is. No machine made by humans can heal itself and adapt in the way that life can, only something made by God can do that.
As you have said yourself, it is inconceivable that something so extraordinary could originate by chance. God has to be involved.
I think you are misunderstanding how this process works.
In a population of bacteria, there are always a small number that are resistant to antibiotics, through natural mutations. Usually, these mutations are actually harmful, so those bacteria do not thrive. For instance, bacteria will naturally encounter low levels of penicillin in the environment, and have a natural ability to produce the penicillinase enzyme to break it down. But a large dose of penicillin when used as a medicine will overwhelm the bacteria and kill them. A bacteria that has a mutation that causes it to over-produce penicillinase will be resistant to those high doses of penicillin - but in normal circumstances that bacteria would be wasting energy producing too much of this enzyme unnecessarily, so will be outcompeted by others. However, when subjected to penicillin as a medicine, all the other bacteria will die and only that one will survive. Its offspring are also resistant to penicillin, so when the population recovers it will be all penicillin resistant. But this is not the addition of a new ability, it is only natural selection. When the antibiotic is removed, any surviving non-resistant bacteria will outcompete the resistant ones, and the population will eventually return to its non-resistant state.
Likewise, if a chemotherapy treatment reduces the number of cancer cells to 1-2%, which cancer cells do you think survived the treatment? The ones which, for some reason or another, were already resistant to the treatment. Clearly they were already resistant, because if they were not they would also be dead just like the other 99%. When those breed up the whole population will have that characteristic. It doesn't mean they evolved a new ability in response to the chemotherapy. It just means that those that already had that feature were selected for.
We use this all the time in farming, as we have to deal with drench resistance in intestinal worms in livestock. If you drench all the animals repeatedly with the same drench (medicine to kill intestinal worms), the few worms that are naturally resistant will be the only ones that survive, and eventually all of the worms on your farm will be resistant and the drench will no longer work. However, if you leave some animals undrenched as "refugia" - places where worms that are not resistant can survive - the population will be continually re-seeded with these susceptible worms. As the susceptible worms are actually fitter in normal circumstances (the resistant ones weren't "better" or "more evolved"), they will outcompete the drench-resistant worms, and ensure that the drench continues to work.
