Hi John, thanks for the reply. I happened to catch your reply before it was done away with, in the meantime(since my friend isn't here), I don't think that they have a big leaning towards solipsism, and honestly speaking, I think it would too. But since they were admittedly quite vague and would naturally want to expand on it, I'll continue the conversation tomorrow and let you know. With that said, everything you mentioned about holistic undetermination and etc. was spot on, this is basically what they mean, or I would construe their strongest position to mean. So I didn't there was anything wrong with your post per se, and I was gonna say that I'd wait for you to knock-it down. But for the meantime, since they're probably sleeping, I wouldn't be able to get anything more out of them, I'll try to clarify what they exactly mean by tomorrow or next week.

Last edited by Dennis (9/05/2015 8:59 pm)

Thanks for that, though I doubt that they would such a stance, and the term subjective was used in some sort of a short-hand, but I'll let you know as soon as I find out. Would it be fair to say that the solipsist is committed to denying the passive reception of the senses?

Well, that made me giggle. My main take is about whether the solipsist position could even be coherently formulated, given that their proposition would require some form of abstraction, and that abstraction would be dependent on some form of reception. If the solipsist is going to deny any form of reception itself, then it's hard to see how this is even slightly plausible or coherent.

Dennis wrote:

Thanks for that, though I doubt that they would such a stance, and the term subjective was used in some sort of a short-hand, but I'll let you know as soon as I find out.

In the meantime, since I already wrote it, here's the reply from earlier again, in case I had him right after all:

Not that I have anything against your friend, but I think we can give a stronger rendition of the problem he mentions. Hopefully, doing so will clarify the problem, thereby the solution.

First, we need a distinction between transient underdetermination and permanent underdetermination. A belief can be transiently underdetermined by all the evidence we have at the moment. It can be permanently underdetermined by all the possible evidence. We're only concerned with permanent underdetermination.

Next, we need a distinction between holistic underdetermination and contrastive underdetermination. Holistic underdetermination is bound up with the view that theories can only be subjected to testing in groups, not in isolation. The idea is that every hypothesis carries with it other assumptions and beliefs about how the world is: about how instruments operate, about causation, about the reality of change, about whether an external world exists. The idea with holistic underdetermination arguments is that we can never determine whether a hypothesis we wish to reject is false, because we can never know whether the fault lies with the hypothesis or with one of the other beliefs built into it; they claim we can always replace one of these beliefs to save the hypothesis.

The view also has the consequence that when we confirm a scientific theory, we confirm that theory along with any metaphysical supposition it includes. If these metaphysical suppositions can be replaced by other metaphysical suppositions, then I think we have a choice between those metaphysical suppositions. If the metaphysical suppositions can't be replaced by other metaphysical suppositions, we call these indispensable to the theory and say we ought to be committed to the reality of those indispensable metaphysical suppositions if we have commitment to (say) the reality of the scientific parts of that theory (ie. theories about electrons). I'm not (and I doubt any of us are) going to deny that scientific theories presume background metaphysical and ontological commitments. But we're going to want to deny the holistic underdetermination argument to avoid relativism about metaphysics. If only one metaphysic is ultimately true, then we're going to want to be able to say that the rest of them are false.

Contrastive underdetermination occurs when there is more than one hypothesis that fits the evidence equally well. So, permanent contrastive underdetermination occurs when there is more than one hypothesis that fits all the possible evidence equally well.

For the contrastive underdetermination argument, consider the conjunction of all empirical truths. Either there aren't multiple completely internally coherent metaphysics that fit the conjunction equally well, or there are. If there aren't, then the conjunction of empirical facts puts constraints on which metaphysic might be correct. If there are, then we open the whole of metaphysics to a contrastive underdetermination argument.

In the first case, since the conjunction of all scientific truths are part of the conjunction of all empirical truths and the latter puts constraints on which metaphysic will be correct, scientific truths put some constraints on which metaphysic might be correct. This is the option for which I think we should argue. 

In the second case, the underdetermination argument just says that given multiple internally coherent metaphysics, m-1, m-2, m-3, ..., that each fit the conjunction of all empirical truths equally well, we have no way of determining which of these metaphysics is correct. If we have no way to determine which of these metaphysics is correct, to be intellectually consistent we ought to remain agnostic about which is correct. Hence, even if we act as if one metaphysic is correct for pragmatic reasons, to be intellectually consistent we ought to remain agnostic about which is genuinely correct. Obviously, the latter case leads to skepticism about metaphysics.

Underdetermination arguments are popular in the debate over scientific realism, where they're leveled against realists about entities like electrons, bosons, fermions. It's going to be worth looking at the replies given to them there. Sorry for any typos.

If it turns out I have the gist of his point after all, then unless someone beats me to dealing with it I'll share my thoughts on all this then.