What has been constant in this overall historical development is a pattern in which at each stage, certain features are regarded as appearance, while others are regarded as of an essence which explains the appearance on a qualitatively different basis. But what is taken as essence at any stage is seen to be appearance of a still more fundamental essence. Ultimately everything plays both the role of appearance and that of essence. If, as we are suggesting, this pattern never comes to an end, then ultimately all of our thought can be regarded as appearance, not to the senses, but to the mind. What science is aiming for is that these appearances be correct, i.e. that the actions flowing from them, such as experiments, be coherent with what the appearances would imply.
Incorrect appearances are thus either mistaken or illusory.
The progress of science then implies the elimination of mistakes and illusions and the development of new sets of related appearances at various levels. Thus with the table to have the appearance of an elliptical object is correct only in a very limited sense. By bringing in the thought that the object is a rigid circle, we obtain a more nearly correct overall set of appearances. The thought of the atomic structure then makes the whole set still more nearly correct and so on. Thus what we are doing is constantly extending the appearances with the aid of thought.