I don't think he is saying, "good explanations are hard to vary while preserving their predictions".
As described above the statement "Everyone just acts in his own interest" very easily preserves its predictive power in a multitude of situations. Indeed, the problem with it is that the statement preserves its predictive power in too many situations! The explanation is consistent with just about whatever happens, so one cannot design a test that makes one believe that the statement is certainly false. So it is too easy to vary and hence a bad explanation.
Evolution does not increase a species' implicit knowledge of the niche by replicating genes. Mutation (evolution's conjectures) creates potential new knowledge of the niche. Selection decreases the "false" implicit conjectures of mutations and previous genetic models of the niche.
So induction does not increase the implicit knowledge of gene sequences.Trial (mutation) and error (falsification) of implicit theories does. This is the process that the critical rationalist says happens but more efficiently with humans.
I think I see where we are disagreeing.
Consider a quantum computer. If the laws of physics say that only our lack of knowledge limits the amount of complexity in a superposition, and the logic of quantum computation suggests that greater complexity of superposition leads to exponentially increased computational capacity for certain types of computation, then it will be quite possible to have a quantum computer sit on a desktop and make more calculations per second than there are atoms in the universe. My quote above from David Deutsch makes that point.... (read more)
“To really make progress here, what we need is a thought-experiment in which a macroscopic superposition is made to yield information about more than one branch, as the counterfactualist rhetoric claims. Unfortunately, your needle-in-the-arm experiment is not there yet, because we haven't gone into the exact details of how it's supposed to work. You can't just say, 'If we did a quantum experiment where we could produce data about glucose levels in someone's bloodstream, without the needle having gone into their arm, why, that would prove that the multivers... (read more)
"What makes this theory a good one is that people have eaten turkeys for Thanksgiving in the past and induction tells us they are likely to do so in the future (absent other data that suggests otherwise like a rise in Veganism or something)."
I do appreciate your honesty in making this assumption. Usually inductivists are less candid (but believe exactly as you do, secretly. We call them crypto-inductivists!)
But there is no law of physics, psychology, economics, or philosophy that says that the future must resemble the past. There also is no law ... (read more)
And if no law of physics precludes something from being done, then only our lack of knowledge prevents it from being done.
So if there are no laws of physics that preclude developing bomb testing and sugar measuring devices, our arguments against this have nothing to do with the laws of physics, but instead have to do with other parameters, like lack of knowledge or cost. So if the laws of physics do not preclude things form happening, we might as well assume that they can happen, in order to learn from the physics of these possible situations.
So for th... (read more)
In the Elitzur-Vaidman bomb test, information about whether the bomb has exploded does not feed into the experiment at any point. When you shoot photons through the interferometer, you are not directly testing whether the bomb would explode or has exploded elsewhere in the multiverse; you are testing whether the sensitive photon detector in the bomb trigger works.
As wnoise said, to directly gather information from a possible history, the history has to end in a physical configuration identical to the one it is being compared with. The two histories repres... (read more)
The Elitzur-Vaidman bomb testing device is an example of a similar phenomenon. What law of physics precludes the construction of a device that measures blood sugar but with the needle (virtually never) penetrating the skin?
"And if the event happens even more when you expect it to then
it is even more evidence for the theory, "
I am not sure you agreed with this based on your response but I will assume that you did. But correct me if I am wrong!
If you did agree, then consider the Bayesian turkey. Every time he gets fed in November, he concludes that his owner really wants what's best for him and likes him, because he enjoys eating and keeps getting food. Every day more food is provided, exactly as he expects given his theory, so he uses Bayesian statistical inference... (read more)
"evidence they've gathered adds up to a sufficiently high probability for P"
Perhaps I should ask what you mean by "evidence"? By evidence do you mean examples of an event happening that corroborates a particular theory that someone holds ?
then you are saying that the event is evidence in favor of the theory. And if the event happens even more when you expect it to then
"For example I don't know how something that is true cannot ever be justified (how else do you know it's true!"
You can't know that something is true. We are fallible. And our best theories are often wrong. We gain knowledge by arguing with each other and trying to point out logical contradictions in our explanations. Experiments can help us to show that competing explanations are wrong (or that ours is!) .
Induction as a scientific methodology has been known (since Hume) to be impossible. Happy to discuss this further if you like. I will cert... (read more)
He does not mean "lacking unnecessary details". For example the statements "Everyone just acts in his own interest" or "Everyone is really an altruist" are simple and lack unnecessary details, explain quite a lot, and are consistent with Occam's razor. But by Deutsch's criteria they are bad explanation because they are too easy to vary.
For example, someone who believes in the self-interest theory could say,
"John gave to charity because he would have felt guilty otherwise. So he really was selfish" .
We see that... (read more)