First of all, we should understand that the subject "existence" in "perceived existence" does not mean all existence. Becker said that the existence of spirit (or mind, soul or self) is imperceptible, but although it is imperceptible, Becker said that spirit exists. So the "existence" in this sentence refers to everything except spirit, so the complete expression should be: except spirit, existence is perceived. Why can't the spirit perceive it? You feel the perception of "color", "pain", "anger" and "joy", but none of them can be called spirit, that is, what you feel is nothing more than a series of special perceptions, and none of them represents spirit, so spirit cannot be perceived. In Becker's case, the spirit can only be said to be perceived by reason rather than sense. )
In this way, stones, houses, mountains, rivers, the sun and so on exist. It is their perception. If you close your eyes, none of this exists. The table in front of you doesn't exist when you look back. It is absurd for Becker to say that they still exist (unless you say that they still exist in the sense that "other spirits are still perceiving them", which is ok). If you only perceive half of the body, it is absurd to say that the other half exists because it is not perceived. In other words, all these things exist inside the mind, and nothing can exist outside the mind. Becquerel called all kinds of things ideas (so the usage of this word is different from that of ordinary people in these philosophers). One of the important reasons is that thoughts exist in the spirit.
When you eat food and wear clothes, clothes and food are just concepts, so Becker said that there is no problem with your concept of eating and wearing (both in the "cerebral cortex"). For Becquerel, it is only a question of language, that is, how to solve the immediate phenomenon. It's just that people get used to a certain language way and change the unaccustomed way. The essence is the same. Just as people are used to writing with a pen, they are not used to writing with a teacup. Of course, the language symbol of a teacup can refer to what the original pen refers to, which is just a habitual problem of language use.