Studying the 4 stages of enlightenment.

https://en.wikipedia.org/wiki/Four_stages_of_enlightenment

Path and Fruit

A Stream-enterer (Sotapanna) is free from:

• 1. Identity view
• 2. Attachment to rites and rituals
• 3. Doubt about the teachings

A Once-returner (Sakadagami) has greatly attenuated:

• 4. Sensual desire
• 5. Ill will

A Non-returner (Anāgāmi) is free from:

• 4. Sensual desire
• 5. Ill will

An Arahant is free from all of the five lower fetters and the five higher fetters, which are:

• 6. Attachment to the four meditative absorptions having form (rupa jhana)
• 7. Attachment to the four formless absorptions (ārupa jhana)
• 8. Conceit
• 9. Restlessness
• 10. Ignorance

The Sutta Pitaka classifies the four levels according to the levels' attainments. In the Sthaviravada and Theravada traditions, which teach that progress in understanding comes all at once, and that 'insight' (abhisamaya) does not come 'gradually' (successively - anapurva),"^[4] this classification is further elaborated, with each of the four levels described as a path to be attained suddenly, followed by the realisation of the fruit of the path.

The process of becoming an Arahat is therefore characterized by four distinct and sudden changes, although in the sutras it says that the path has a gradual development, with gnosis only after a long stretch, just as the ocean has a gradual shelf, a gradual inclination with a sudden drop only after a long stretch. The Mahasanghika had the doctrine of ekaksana-citt, "according to which a Buddha knows everything in a single thought-instant" (Gomez 1991, p. 69). The same stance is taken in Chan Buddhism, although the Chán school harmonized this point of view with the need for gradual training after the initial insight.^{[citation needed]} This "gradual training" is expressed in teachings as the Five ranks of enlightenment, Ten Ox-Herding Pictures which detail the steps on the Path, The Three mysterious Gates of Linji, and the Four Ways of Knowing of Hakuin. The same stance is taken in the contemporary Vipassana movement, especially the so-called "New Burmese Method"