The belief that all concepts are plausible, and that believing otherwise requires either eschewism or denial.
If you were to define it in an anthropic and logical context, you would say that it is the belief that any conceivable idea may be true, but since alplausism transcends humans and logic, most people find this definition unsatisfactory, and since they usually are unable to come up with any other concise definition, they end up requiring the use of several paragraphs of examples to describe it.
One of the key features of alplausism is that it also allows the plausibility of the concept that alplausism false, as well as any other objections and oppositions to it or its consequences, no matter how illogical or ridiculous it is to do so. In this respect, it is similar to solipsism.
While alplausism is the actual core belief of any true alplausist, some of them may employ eschewism in order to have some sort of substitute beliefs that relate to the actual world they live in and can be affected by, though they'll still argue till their last dying breath that such-and-such which contradicts their observed reality is possible.
The use of the 3 particular assumptions described below, so as to make sense of the world. They are:
1) Reality does exist.
2) A demonstration of an idea can indicate the idea is true/conforms to reality.
3) As the amount of tests of an idea increases, and the proportion of outcomes that demonstrate the idea increases, the likelihood of the idea's truth increases.
Eschewism gains its name from the fact it can eschew many ridiculous and/or unhelpful beliefs, such as solipsism, by constricting the domain of what's considered true to that which matches observations. And you could probably say that science is essentially built upon the employment of eschewism to create accurate predictions with which to navigate one's experience. With this in mind, we can consider eschewism as sort of a cross between Newton's Flaming Laser Sword and the Scientific Method.