such that, if our external senses were sharpened to the highest degree, it could be perceived; though it can never be presented in any observation or experiment. To assume [the existence of] rational inhabitants of other planets is a thing of opinion; for if we could come closer to them, which is in itself possible, we should decide by experience whether they did or did not exist; but as we shall never come so near, it remains in the region of opinion. But to hold the opinion that there are in the material universe pure thinking spirits without bodies (viz. if we dismiss as unworthy of our notice certain phenomena which have been published as actual) is to be called poetic fiction.

This is no thing of opinion, but a mere Idea which remains over, when we remove from a thinking being everything material, and