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If you open the new NCERT Class 9 science textbook at the chapter "Journey Inside the Atom", the first name you meet is not Dalton or Rutherford. It is Acharya Kanada. Many students then hear two exaggerated stories: that ancient India "discovered the atom", or that the idea was just mythology. Neither is right. This post explains what Kanada's school actually argued, why the argument is clever, and how it differs from the atomic theory you will be examined on.
Who was Kanada?
Very little is known about Kanada as a person. The Stanford Encyclopedia of Philosophy entry on ancient atomism describes him as "regarded as founder of the Vaiśeṣika school", and says the beginnings of Indian atomism are hard to date but "likely" go back several centuries before the common era. The first surviving commentary on his work is by a later author, Praśastapāda.
The NCERT Class 9 textbook (Exploration, first edition April 2026), Chapter 8 places Kanada "more than 2,000 years" back and says his ideas are recorded in the Sanskrit text the Vaisesika Sutras. Treat any precise birth year you see online with suspicion; the sources do not support one.
What did the Vaisesika school say matter is made of?
The school was mainly interested in ontology, the study of what kinds of things exist. The Internet Encyclopedia of Philosophy article on Nyāya, the sister school that adopted much of this system, lists its categories: substance, quality, action, universal, individuator, inherence and absence. Atoms sit inside the first category, substance.
According to the SEP entry on naturalism in Indian philosophy, Nyāya-Vaiśeṣika thinkers held that there are atoms of four elements, earth, water, fire and air. These atoms have the smallest possible magnitude, are spherical, indivisible and eternal. Composite things made from them are not eternal, because every product eventually breaks up. Unlike the Greek atomists, they gave atoms real sensible qualities: water atoms, for example, were thought to carry coldness.
The same SEP entry describes a fixed order of combination. Two atoms of the same type form a dyad (dvyaṇuka). Three dyads form a triad (tryaṇuka), which was held to be the smallest thing you can perceive. Your NCERT book simplifies this to "groups of two" and "groups of three" paramanus. If you meet both versions, that is why.
Why did they think division must stop?
This is the most interesting part, and it is worth learning as an argument. The SEP naturalism entry sets it out. Suppose every visible thing could be divided into parts, and those parts divided again, forever. Then a mountain and a mustard seed would both contain an infinite number of parts. In that case, the argument runs, they would be equal in size, which is absurd. So division must end in partless pieces: atoms.
The school also argued that division needs something to divide. A process of division that destroyed its own base would be, in the encyclopedia's phrase, "as absurd a notion as digging a hole in empty space".
Notice what kind of reasoning this is. It is a reductio ad absurdum: assume the opposite, follow it to a contradiction, and conclude your claim. You use exactly this method when you prove that the square root of 2 is irrational.
A modern mathematician would push back. Infinite sets can differ in a way that a count of parts does not capture, and a line 1 cm long and a line 1 km long both contain infinitely many points. The SEP atomism entry notes that the argument rests on a paradox about infinite division of the kind also found in the ancient Greek tradition, and that it was closely echoed in later Islamic debates.
How is this different from Dalton's atomic theory?
Here is the line to remember for exams. The NCERT chapter says Kanada's description "does not specify the proportions in which parmanus combine to form different substances", and that the concept of the atom "originated as an imaginary idea rather than from experimental observations". It then credits John Dalton, in 1808, with the first scientific description, because his theory was built on the measured masses of reacting substances.
The SEP atomism entry makes a similar point from inside the tradition: Nyāya-Vaiśeṣika atomism "was only based on logical inference and could not be confirmed by experience". Thinkers in the school answered that composite things are real even when their parts are invisible, pointing out that a forest can be seen from a distance where the individual trees cannot.
So the fair summary is this. Kanada's school asked the right question, gave a sharp argument for a limit to division, and built a detailed theory of how small units combine. It did not measure anything, and it could not decide between rival pictures. That took chemistry. Our post on Dalton's atomic theory picks up the story there, and our post on Democritus and Greek atomism shows a parallel tradition with different assumptions.
What can a student take from Kanada's way of working?
Follow an assumption all the way. The mustard-seed argument works by taking "infinite division" seriously and seeing where it leads. Try this on any claim in a chapter: what would follow if it were false?
Separate an argument from evidence. A good argument can still be wrong. Ask of every idea in science: how was this tested?
Read sources at the right resolution. Your textbook's "groups of three" and the classical "three dyads" are both reports of one theory at different levels of detail.
If the step from paramanu to protons, neutrons and electrons feels like a jump, take it one idea at a time. The Fermi Concept Library covers every concept in physics, chemistry, biology, mathematics and computing, so you can go from "law of constant proportions" to "atomic number" in order.
Next step: write the mountain-and-mustard-seed argument in your own words in four lines, then write one sentence on what experiment could have tested it.
