The Tiantai school divided the Buddha’s fifty years of teaching into five periods of varying degrees of profundity. The first period occurred during the first few weeks that Śākyamuni Buddha sat beneath the Bodhi Tree. During that time, he taught the Flower Garland Sūtra, although Nichiren points out later in Kaimoku-shō that it would be more accurate to say that it was the bodhisattvas who were present that actually did the teaching. Starting with the discourse on the Four Noble Truths taught at the Deer Park to the five ascetics, Śākyamuni Buddha spent twelve years teaching the pre-Mahāyāna (aka Hinayāna) teachings found in the Āgama sūtras. After that he spent eight years teaching the preliminary Mahāyāna teachings of the Vaipulya or Expanded sūtras. He taught the Perfection of Wisdom sūtras during the twenty-two years that followed that. For the last eight years of his life, the Buddha taught the Lotus Sūtra. On the very last day and night of his life the Buddha taught the Mahāyāna Mahāparinirvāṇa Sūtra. It should be noted that even Nichiren points out in other writings that these time spans are uncertain. In any case, modern textual scholarship would dismiss all of this as arbitrary, especially since the Mahāyāna sūtras are now seen as compositions arising after the Buddha’s lifetime. Nevertheless, Mahāyāna Buddhism accepts these sūtras as embodying the word of the Buddha in the sense that they convey the full depths of the Buddha’s insight and compassion. The Tiantai system of classifying the sūtras into five periods of teaching can still be seen as a useful way of approaching the sūtras in terms of how they build upon one another and lead those who put them into practice into deeper and subtler insights.

The Buddha was not concerned with affirming or denying any kind of God. What the Buddha constantly taught was for the purpose of helping people understand suffering, cut off the causes of suffering, realize the cessation of suffering, and follow the path to the cessation of suffering. Anything within the six worlds of transmigration, including the heavenly realms where gods of varying degrees of sublimity reside, was still within the purview of suffering and its causes. While union with God is looked upon as a worthy and attainable goal, it is not the final goal, for it is still involved in the impermanent flow of causes and conditions. Only the unconditioned peace of nirvāṇa can provide true peace according to the Buddha.

We might wonder if Buddhism itself has anything to say about monotheism or religion based upon revelation and salvation by a transcendent God. Actually, throughout the Pāli canon, the Buddha did teach a lot of things that are relevant to the claims of Western monotheism. To begin with, the three Western monotheistic traditions all base themselves upon some form of revelation wherein God speaks to humanity. The Buddha, however, saw all teachings based on revelation, tradition, hearsay, or any other system of authority not based on direct experience as doubtful. The Buddha’s teachings about this were famously expressed in the following exchange between himself and the Kalama people of the town of Kesaputta:

“There are, Lord, some ascetics and brahmins who come to Kesaputta. They explain and elucidate their own doctrines, but disparage, debunk, revile and vilify the doctrines of others. But then some other ascetics and brahmins come to Kesaputta, and they too explain and elucidate their own doctrines, but disparage, debunk, revile and vilify the doctrines of others. For us, Lord, there is perplexity and doubt as to which of these good ascetics speak truth and which speak falsehood?”

“It is fitting for you to be perplexed, O Kalamas, it is fitting for you to be in doubt. Doubt has arisen in you about a perplexing matter. Come, Kalamas. Do not go by oral tradition, by lineage of teaching, by hearsay, by a collection of scriptures, by logical reasoning, by inferential reasoning, by a reflection on reasons, by the acceptance of a view after pondering it, by the seeming competence of a speaker, or because you think: The ascetic is our teacher.’ But when you know for yourselves, ‘These things are unwholesome, these things are blamable; these things are censured by the wise; these things if undertaken and practiced lead to harm and suffering’, then you should abandon them. “

The most important and far-reaching difference between the Buddha and Brahmanism is that he did not speak of Ātman and Brahman, but instead taught the doctrine of anātman or no-self. Instead of teaching people to discern a permanent, fixed, independent selfhood, the Buddha taught how to relinquish attachment to self by pointing out that the self is just a label given to the five ever changing and mutually interdependent aggregates of form, feeling, perception, mental formations, and consciousness. The Buddha pointed out that none of these five aggregates has any permanence. They all function in a constant state of flux. Additionally, they must all function in tandem. Any one of the five aggregates would be unable to exist without the other four. This lack of a stable basis for existence precludes any kind of peace or security that depends on something substantial and abiding. The life of the five aggregates is a dynamic interrelated process, and one who seeks some uninterrupted satisfaction from this process will only find suffering instead. Because the five aggregates are impermanent and lead to suffering, they are said to be without a self. Specifically, this means that one cannot attribute to them the permanently abiding and happy self that was the goal of the religious sages and mystics of the Upanishads. A provisional self can be attributed in an abstract way to the life process, but an actual thing or substance called a self cannot be found within the process. Nor can one meaningfully talk about a self apart from the five aggregates because such a self would be a mere abstraction with no substance or empirical reality to back it up. The conclusion is that the five aggregates of form, feeling, perception, mental formations, and consciousness are characterized by the three marks of impermanence, suffering and non-self. In this way, the Buddha revealed the vanity of the idea of a permanently abiding happy self. Once one ceases to think in terms of such a self, then one is free from all the compulsions, fears and desires that go along with the assumption that there is such a self to find, protect, or appease. One then becomes an arhat, or “worthy one,” who will no longer suffer from the cycle of birth and death.

There is also much in the Vedic worldview that carries over into Buddhism. The law of karma carries over, though the Buddha refined it and put the emphasis on the intentions behind purposeful action when determining whether a given act is wholesome or unwholesome. The various beings and worlds of the Vedic cosmology carried over and this eventually became the six paths of rebirth in Buddhism (the hell-dwellers, hungry ghosts, animals, fighting demons, humans, and heavenly beings), though the Buddha would propose a way to escape the round of rebirth among these six worlds. The Buddha certainly agreed with the Upanishadic sages that the benefits of the Vedic sacrifices, worldly wealth and rebirth in the heavens, were temporary at best and that a more transcendental goal was needed.

Not everything carried over, however. The Buddha did not agree with the system of the four classes (what became the basis of the caste system) and frequently argued with brahmins who believed that they were superior simply by virtue of being born as brahmins, whereas the Buddha pointed out that it is only by virtuous deeds that one could claim to be pure and worthy of honor. The Buddha also did away with the more extreme and harmful forms of asceticism like wearing no clothes, fasting to the point of starvation, or subjecting oneself to the five fires (sitting in the middle of four bonfires with the hot summer sun overhead as the fifth fire). Instead he proposed a set of dhūta (lit. “shaking off’), twelve relatively mild austerities such as keeping only three robes, or only eating once a day, or sleeping under the open sky. The dhūta were a voluntary practice for those monks and nuns who felt the need for such extra discipline to help shake off the habits of self-indulgence. Note that in the Lotus Sūtra it says that one who keeps the sūtra even for a moment “should be considered to have already observed the precepts and practiced the dhūta.” Finally, although the Buddha did teach the methods of yogic concentration that he had learned from Ārāda Kālāma and Rudraka Rāmaputra, he taught the yogic methods only to provide a means to concentrate the mind in preparation for the distinctive Buddhist practice of “insight” (Skt. vipa’yanā; Ch. kuan; J. kan) meditation and as a form of peaceful abiding for the arhats. By itself, the yogic discipline only leads to the meditative absorptions known as the four dhyānas (Ch. ch’an; J. zen) and other states of deep concentration. These states were only temporary respites as were the heavenly rebirths that corresponded to their cultivation. This has been discussed in regard to the wrong views relating to eternity in the Buddha’s Supreme Net Discourse.