When we worship gods or Buddhas, we begin with the phrase of “namu.” Namu is an Indian word that has come to mean “offering of life to Buddhas and gods” in China and Japan. Our social standing is determined in part by possessing a spouse and children, retainers, fiefs, and gold and silver, though some people do not have these. Regardless of whether we possess these or not, no one possesses treasure more precious than life. Accordingly, sages and wise men in the past have donated their lives to the Buddhas in order to attain Buddhahood.

That is to say, Young Ascetic in the Snow Mountains offered his own body to a demon in order to learn a holy teaching consisting of eight Chinese characters. Medicine King Bodhisattva burned his own elbow and offered it to the Lotus Sūtra as a light. In Japan, Prince Shōtoku peeled the skin of his own hand to write the Lotus Sūtra on it, and Emperor Tenchi burned his third finger as an offering to Śākyamuni Buddha. These are deeds of sages and wise men, which are impossible for us ordinary people to emulate.

Nevertheless, ordinary people can become Buddhas by fully understanding the meaning of the word of “kokorozashi (intention)” and practicing it. What is the intention? When we consider this in detail, it refers to the doctrine of spiritual contemplation. What does the doctrine of spiritual contemplation mean? It means the way of practicing the teaching of the Buddha according to the intent of the Buddha, not necessarily according to what is literally said in the sutra. For example, if a man donates his only set of clothes, which he wears for the cause of the Lotus Sūtra, this is the same as peeling his own skin for the sake of the Dharma. Suppose there is a man during the time of a famine who offers to the Buddha the only food he has to stay alive for a day. This is the same as offering his life to the Buddha.

These offerings are as meritorious as the offering of an elbow by Medicine King Bodhisattva or the offering by Young Ascetic in the Snow Mountains of his own body to a demon. Therefore, we can say that the self-sacrificial offerings of sages are phenomenal whereas the offerings of ordinary people according to the intent of the Buddha are noumenal. The doctrine of offering, one of the six practices for bodhisattvas to attain enlightenment, preached in the Great Concentration and Insight, part seven, refers to this noumenal offering, i.e. the practice of offering according to the intent of the Buddha.

Jiri Kyuō Gosho, Phenomenal Offering and Noumenal Offering, Writings of Nichiren Shōnin, Faith and Practice, Volume 4, Page 98

Intention is something I find vital in all things. I see this Intention reflected in the Lotus Sūtra in the latter half of Chapter 2, Expedients:

Those who, after the extinction of a Buddha,
Were good and gentle,
Have already attained
The enlightenment of the Buddha.

Those who, after the extinction of a Buddha,
Erected billions of stupas,
And who purely and extensively adorned [those stupas]
With treasures
Such as gold, silver, crystal,
Shell, agate, ruby, and lapis lazuli,
And who offered those adornments to his śarīras;
Or those who made the mausoleum [of the Buddha]
With stone, bricks, or clay,
Or with many kinds of wood,
Such as candana, aloes, or agalloch;
Or those who made the mausoleum of the Buddha
With heaps of earth
In the wilderness;
Or the boys who made the stupa of the Buddha
With heaps of sand by playing,
Have already attained
The enlightenment of the Buddha.

Those who carved an image of the Buddha
With the [proper] physical marks in his honor
Have already attained
The enlightenment of the Buddha.

Those who made an image of the Buddha
With the seven treasures;
Or those who made it
Of copper, copper-gold alloy, nickel,
Pewter lead, tin, iron, wood, or clay;
Or those who made it in plaster work,
Have already attained
The enlightenment of the Buddha.

Those who drew or caused others to draw in color
A picture of the Buddha adorned with his physical marks,
Each mark representing one hundred merits,
Have already attained the enlightenment of the Buddha.

The boys who by playing drew
A picture of the Buddha
With a piece of grass or wood,
Or with a brush,
Or with the back of their fingernails,
Became able to accumulate merits one by one.
Having great compassion towards others,
They attained the enlightenment of the Buddha,
Taught only Bodhisattvas,
And saved many living beings.

Those who respectfully offered
Flowers, incense, streamers, and canopies
Enshrined in a stupa-mausoleum;
Or those who caused men to make music
By beating drums, by blowing horns and conches,
And by playing reed-pipes, flutes, lyres, harps,
Lutes, gongs, and copper cymbals,
And offered the wonderful sounds produced thereby
To the image or picture of the Buddha;
Or those who sang joyfully in praise of him for his virtues;
Or those who just murmured [in praise of him],
Have already attained
The enlightenment of the Buddha.

Those who, without concentrating their minds,
Offered nothing but a flower to the picture of the Buddha,
Became able to see
Innumerable Buddhas one after another.

Those who bowed to the image of the Buddha,
Or just joined their hands together towards it,
Or raised only one hand towards it,
Or bent their head a little towards it
And offered the bending to it,
Became able to see innumerable Buddhas one after another.
They attained unsurpassed enlightenment,
Saved countless living beings,
And entered into the Nirvana-without-remainder
Just as fire dies out when wood is gone.

Those who entered a stupa-mausoleum
And said only once “Namo Buddhaya,”
Without even concentrating their minds,
Have already attained the enlightenment of the Buddha.

Those who heard the Dharma
In the lifetime of a past Buddha
Or after his extinction
Have already attained the enlightenment of the Buddha.

By definition, a Noumenal Offering is “[an offering] as it is in itself, as distinct from [an offering] as it is knowable by the senses through phenomenal attributes.” Or, in other words, the Intention.

See also Small Good Deeds from the Introduction to the Lotus Sutra.