So, on what basis do you believe that this argument is valid:

1. If P, then Q
2. P
3. Therefore, Q

Look, put down your book of fallacy titles and get real. Present a deductively valid argument that has the negation of my premise as a conclusion and that has premises that are more plausible than any of mine.
If you can't do that - and you won't be able to - I'll accept that there is a reasonable doubt about its truth.

Premise 1 is self-evidently true. It is not self-evidently true to those with limited powers of reflection, of course, or to cats, or the insane. But it is self-evidently true and it is appealed to by all of those who engage in serious intellectual inquiry.

But by all means show me to be wrong. Just try and do so without being insane.

Premise 1 is self-evidently true. It is not self-evidently true to those with limited powers of reflection, of course, or to cats, or the insane. But it is self-evidently true and it is appealed to by all of those who engage in serious intellectual inquiry. — Bartricks

So your support is basically, "Either you accept this without question or you suck."

Great argument.

If you're not religious you should be. You have their argumentation skills.

Show it, don't spray it.

Show me how to argue well, Terrapin. Present a deductively valid argument that has the negation of one of my premises as a conclusion and premises of its own that are more prima facie plausible than mine.
Oh, of course, first you need to scurry around the internet looking up what those words mean....

Get back to me when you hit puberty.

All talk, no trouser.

Like most narcissists you think that the test of whether someone can argue well is whether they say things you agree with. Infant.

Your style is basically asshole with a lot of attitude. It's kind of pointless to pretend that I'd have a fruitful discussion about philosophy with that stereotypical personality. It sucks that the Internet is full of that, but there it is.

Arrr, are you feeling stupid? Make an argument Terrapin and stop blubbing you self-centred snowflake.

I did make an argument. I don't accept your premise. It's fallacious. You have no support of it except for the brashness of "It's self-evident if you're not a moron/not insane." We'll get nowhere like that.

Randroids kind of argue like that, too.

"Terrapin does not accept something, therefore it is false" is not evidence. It's an absurd principle that has nothing to be said for it.

If ten people report that the criminal was wearing a red hat, that's good evidence the criminal was wearing a red hat.

Not to you though. No, someone who reasons like that has committed a fallacy according to you - which means it must be true that they have.

You don't have any arguing skills, Terrapin. Present an actual argument and stop thinking that if you deny or don't accept something, that constitutes good evidence that the proposition in question is false.

Labels and assertions, that's all you've got.
Express everything in the form of a deductively valid argument or say nothing.

So , dispensing with all of the attitude nonsense, which isn't going to help you in any way, you need to realize that some people are not going to accept some or all of your premises.

If all you have in support of your premises is arguing that they're self-evident, then you're basically always going to be preaching to the choir. (Assuming that you're getting simple stuff like modus ponens right after you state your premises.)

You can do that, of course, but I don't know if there's much of value in it. (Unless it simply makes you feel better about yourself or something and that's really the point.)

Otherwise, you need to find more nuanced, creative, fruitful ways to deal with the fact that your premises might be rejected. Simply insulting the rejectors, framing things as if the people rejecting premises are morons who are vastly inferior to your "philosophical expertise," etc., won't do it if your goal is to persuade anyone who doesn't already agree with you.

Argument - present an argument.

Or don't take the advice. It doesn't matter to me. I just thought you might have a goal of wanting to persuade people who don't already agree with you. But I guess not.

Present an argument. Your advice is terrible and I don't want it. Now, present an argument for something. Don't express your feelings, don't give me advice about the world and other people. Just present an argument.

Hard, isn't it? Hard to actually argue, much easier to dispense condescending advice and attack personalities.

No it isn't. You're begging the question because you're just assuming that the mind is a material thing - a brain. Yet what the mind is is the issue under investigation. So you need to present an argument that has 'therefore, the mind is material' as a conclusion but not a premise.

If you can do that, and if the premises of the argument are sufficiently self-evident (or themselves derived from sufficiently self-evident truths) then you will have provided rational inquirers with some reason to believe that minds are divisible, and thus some reason to doubt whether the rational intuitions that represent our minds to be indivisible are accurate. But until or unless you do that, you're just begging the question by dogmatically assuming that you already know what the mind is, regardless of the evidence.

What's hard is learning that arguments aren't just simple instantiations of modus ponens, or even necessarily deductive.

Make an argument.

You've looked some words up. Well done. Now make an argument. it's hard - hard to make a good one. Try.

Maybe try cranking down the attitude a bit until you get to a point where you don't figure that everyone needs to look up simple terms of art?

try making an argument.

1. If an object is material, then it is divisible
2. My mind is not divisible
3. Therefore my mind is not material — Bartricks

The argument needs some improvement:

1. If an object is material, then it is divisible into quanta; however, the Planck size is the absolute small size limit beneath which the quantum is no longer divisible. All has been quantized so far except space-time gravity, this effort being just barely underway by loop quantum gravity hoping to achieve space-time quanta. There is no continuum in nature, as Einstein thought, but his theory still holds at large numbers of grains. Also, even the smallest quantum has extension—the Plank size. See for time—the Plank time. One could still argue that the ultimate basis of the covariant quantum fields are continuous waves, but above that quanta come into play. As an aside, the waves are good for a TOE, in that the ultimate basis cannot have parts.

Field quanta are the key to the once mysterious 2-slit experiment: even sending one particle at a time builds up an interference pattern, thus, the particle is a field of waves of energy. Mass is equivalent to mass which approximates energy being equivalent to matter.

2. My mind is not divisible. The objects of consciousness, as what is currently on/in the mind are indeed unified, these called qualia, and are also smoothly stitched onto previous qualia. These qualia match external and internal inputs, mostly, with the proviso that a more useful face has been painted on them. This representation takes time, as so did the figuring of the thought, action, or scene produced. So, then, the inputs to the mind are divisible, at least. Note that systems always have parts. 'More' is always different: one neuron alone can't do anything but when there are more then connections become. The brain doesn't have two hundred neuron connections for nothing—these to be ignored because the mind is proposed to have a separate apparatus and separate information.

Consciousness/mind is therefore too late in the process to be able to do any figuring on its own; it always shows the past, but this does not crush the ability of qualia to be useful, since evolution doesn't spend great expense for nothing, especially that which had so much time and energy invested over millions of years. One proposed usage is that to know and record what went on is best and most quickly done through this self-developed symbolic language of qualia. As such, other figuring areas can then check in immediately or later, expanding on it, if need be, as rumination, deliberation, and such.

3. Therefore my mind is not material. This isn't known, even by itself, and also it doesn't necessarily follow here from (1) and (2). Whatever is proposed as immaterial, intangible, transcendent, and the like as distinct, would still have to exchange material energy with the physical/material realm and speak its language, making it not really distinct. Research continues, but so far the physical does it all. It has to be said, though, that conscious qualia would seem to be of a fantastic process. Unfortunately, it is difficult if not impossible to get at the private internal first person experience from the public external third person.

this is a reply to your first point.

You're confusing the smallest things scientists need to posit with 'indivisible' things. A common mistake. Take the smallest thing that is extended in space. Now divide it. It has nothing to do with size. It has to do with the fact that extended things occupy some space and any - any - region of space is divisible.

So, you haven't challenged premise 1. What you've done is this: 'sciency, sciency, sciency, science - therefore premise 1 is false". This is metaphysics, not science.

This is a reply to your 2. I don't understand what you mean. Why are you talking about qualia? I said the MIND is indivisible. This is something our reason represents to be the case.

For instance, have you ever attributed half a mind to a person? What would that even mean?

Premise 2 is supported by our rational intuitions and so you need countervailing evidence that it is false. What you must not do is just assume that the mind is the brain and then tell me all about how divisible the brain is. You need an argument that has "the mind is a material object" as a conclusion and premises that are more plausible than mine. Then you'll have provided rational inquirers with a reason to think there's a reasonable doubt to be had about the intuitions in support of premise 2. Unless you do that you're just assuming the mind is the brain - or some other extended thing - not showing it to be.