Solipsism, Nihilism, Radical Constructivism, and Metaphysics

I find solipsism very interesting, mostly because it's absolutely ridiculous. Solipsists believe that they are the only thing that they are certain exists. Because if you are thinking about you existence you are existing (or something to that extent). Con ego sum. It's kind of an egotistical statement though, don't you think? It's giving ones self way too much credit. Do you you think you could have imagined all the things in the world? all the intricate details, all the people you meet -- it is all in your dream?

Philosophical nihilism is the idea that nothing really exists, values have no value, and nothing can be truly known.

Like I mentioned in my last post, in psychiatry nihilism is a delusion. ( A delusion is a distorted belief, not to be confused with a hallucination which is sensory experience not caused by external stimuli.) This delusion is found in certain types of schizophrenia; the patient may think that they are a ghost and only here in spirit form.

Radical constructivists believe that knowledge adjusts itself to fit certain situations. We cannot know what we have not experienced. Yet, it is not through our direct experiences that we construct our world, but our interpretations, it's what we take from our experiences that shapes our world and knowledge. "one need not to enter far into constructivists thought to realize that it inevitably leads to the contention that man --and man alone -- is responsible for his thinking, his knowledge and, therefore, also for what he does" (Glasersfeld).

Kant stated that, metaphysics suggests that things are only true if they correspond to an independent and objective reality.

So the difference between solipsism and nihilism is that solipsists state that they are real and everything else isn't, where (metaphysical) nihilists suggest that nothing is real including themselves. The idea's of Radical constructivists and solipsists overlap, but solipsist deal with the metaphysical -- a realm radical constructivists want nothing to do with.

According to Glasersfeld, our interpretations of reality constructs our knowledge. In class it was stated that RC, unlike solipsists, believe that you can't construct the world any way you want. Yet, since RC don't believe in metaphysics, wouldn't that suggest that you can construct the world anyway you want? Do any of the four philosophical positions/beliefs cross over in any other way?