Next, let’s investigate“Those who excell in an art(gei) are well-informed in everything.” The dictionary has the following such:

Those who have understood the mysteries of any art, also know the road to truth in other fields.

That there is a big difference in the meaning of gei as previously explained is self-evident. Gei is not a mere hobby or pastime, neither does it have a meaning of way of livelihood. The mysteries of the geido of Tea and other arts show a strong spirituality that is like to a path upon which one the struggles. In this, some people think it’s basis has the same meaning as mastering gei, that is, mastering being a human.
For example, the late Edo period tea master, Ii Naosuke wrote the following in his “Beginner’s Record”:

The way of drinking tea is the art of cultivating the heart, so that a spiritual life does not escape us.

Here, when we master the mysteries of chado, we are not disconnected from all methods and truths, unlimited to chado. Posessing gei implies a universality.
Also, the next is from the “Record of Zen Tea: Matters of Practicing Tea”:

The original meaning of Tea is not about choosing good or bad utensils, not about debating skill in making tea. It is simply an ascetic practice, where we treat the utensils carefully, concentrate intensely, and contemplating our true character. What we entrust to tea is nothing other than labouring to seek our own true character.

The original meaning of chado is not only discussing what dogu are good or bad or discussing one’s form when making tea. It means simply that by concentrating your heart on one utensil at a time, you can realize the true character. Chado is nothing more than training to seek your own true character. In short, realizing the true nature of things results in the comprehension (satori) of Buddhism. This is a situation of knowing the nature of all truths. That is what this means.