The Relationship Between Idealism And Solipsism

It's been a while since I directly addressed idealism, and I've been wanting to emphasize the way that idealism, in many cases, ultimately collapses into solipsism, with solipsism (by most definitions) being objectively false.  I will revisit some earlier points on idealism, the external world, and solipsism before elaborating on how idealism can be just repackaged solipsism.

Idealism, or at least a major variation of it, is the concept that there is no such thing as matter, only mind(s).  This is bullshit, as I will demonstrate.  In less extreme forms, it holds that the external world is not mind-independent, i.e. that the external world exists, but only because a mind perceives it.  There really is physical matter outside of my consciousness and I cannot be mistaken about this.  Any manifestation of idealism that says nothing material exists is complete nonsense, and it takes only a few moments of reflection and experience with my sense of touch to dispel such a fallacious myth with absolute certainty.

For if I did not have a body I could not experience physical sensations at all, and I experience physical sensations; therefore, it follows by necessity that I have a physical body, and from this I am able to soon discover that my body is in contact with external physical stimuli [1].  I know only what I perceive my body and the external world beyond it to look like, though, and thus I do not know what their actual appearances are.

It must also be acknowledged that something besides matter and my consciousness does exist--logic.  Axioms and logical truths are mind-independent, even if matter is not.  This means that it is possible that if I or the uncaused cause ceased to exist then the physical world would vanish, but it is impossible for logic to only exist as a function or side-effect of a consciousness.  Truth and logic exist abstractly whether or not any minds at all exist to grasp or recognize them.  They are necessarily mind-independent.

Now, onward to solipsism.  There are two types of metaphysical solipsism: the first claims that nothing but one's mind exists (the epistemological version of this states that only one's mind can be known to exist), and the second claims that there are no other minds besides one's own.  The latter is very distinct from the former, since the nonexistence of other minds does not mean the nonexistence of the external world, time, or other things besides one's consciousness.

The former is impossible not just because there really is matter outside of my own mind, but also because logic itself is not a part of my mind, only grasped by it, and would exist even if my mind did not.  If the first metaphysical solipsism says that only my mind exists, and logic is something other than my mind, then it cannot be true and I do not even need to prove that matter exists to refute this kind of solipsism in full.  As I have explained before, "My mind alone is not all that exists, but it might be the only mind that exists" [2].

Some forms of idealism quickly reduce down to a form of mere solipsism, since they both hold that a mind exists and, at the very least, that nothing actually exists apart from a mind (or at least no matter).  It is fairly easy to see how idealism can lead to solipsism.  In this sense, as readers can see from how I addressed each, refuting a certain kind of idealism and a certain kind of solipsism can involve a very similar process.  At minimum there is something nonphysical and abstract outside of my consciousness and matter does exist.

[1].  See here:
A.  https://thechristianrationalist.blogspot.com/2017/08/the-external-world.html
B.  https://thechristianrationalist.blogspot.com/2017/07/dreams-and-consciousness.html

[2].  https://thechristianrationalist.blogspot.com/2017/12/solipsistic-phenomenology.html