Zhiyi emphasizes the idea that a whole universe of three thousand worlds is enveloped within a micro-world of a single experience, and the micro-world of a single experience penetrates the whole universe of three thousand worlds.

First, everything in the universe is divided into ten classes or worlds, from the state of hell to the state of being a buddha. Zhiyi holds that these ten worlds do not exist independently but are interrelated, and he maintains that each of these ten worlds contains ten worlds. In this way, he posits one hundred worlds.

Furthermore, Kumarajiva’s version of chapter 2 of the Lotus Sutra teaches that all things are conditioned by ten categories or factors. One hundred worlds multiplied by these ten factors makes one thousand. Further, if we look at a single thing, we can see that it is constituted by its autonomy (individual existence), the five mental and physical components which constitute it, and by its environment. The one thousand multiplied by these three spheres makes three thousand. In brief, “three thousand” is a skillful way to express the weaving together of the entire cosmos.

In contrast, a single occasion of experience can point to the smallest, infinitesimal world. It can express either an entity or a subject, something both temporally and spatially infinitesimal, and not necessarily subjective. Zhiyi insisted on this. His use of terms such as “a single experience” or “one subject” is derived from his respect for the power of engagement with existence. With regard to mutual penetration of three thousand worlds in one occasion of experience:

Also, we do not say that a single subject exists first and then all things afterward, nor do we say that all things exist and then such a subject. … Both before and after are impossible. … If all things emerge from one subject, this is only the warp; if a subject includes all things in a moment, this is only the woof: either is impossible by itself. A single subject is simply all things, and all things are really one subject.

Thus, one should not discuss either the three thousand things or the moment of experience from the point of view of such things as essence and appearance, real and nonreal, whole and part, or in terms of such things as temporally or spatially before and after, primary and secondary, superior and subordinate, or same and different.

The powers of all things in the universe cohere together and are united. The power of one thing, moreover, spreads out and becomes fully present within all things. If we seek the boundary of the largest universe, we will know that it is infinitely expanding. Yet at the same time, if we magnify the smallest particle with a microscope, we will know that it is the infinite, entire universe. Thus the microcosm is the macrocosm, as it is, and vice versa. “A subject is all things, and all things are subjects.” The reality of this kind of world and existence is beyond our limited ability to comprehend such things as being and nonbeing or large and small. In this sense, this is a mysterious world. “Profoundly wonderful and profoundly deep, it is beyond understanding. It is beyond words. That is why it constitutes a mysterious state.”