In ontology, we saw that the universe is made up of concepts and relations. We have also seen that the relations can be expressed as propositions of Facts or General Principles. But a fact can  be true, false or partially true.

Examples:
1. If someone says that ‘Sahara Desert is in India.’ It is a False statement.
2. Or if someone says that ‘Water turns into gold on heating’, it is a False General Principle.

• How does one know that a certain Fact or General Principle really exists or not?
• In other words, what is the reason for believing in something to be the case?
• What is the evidence or proof of a certain Fact or General Principle?

This is the subject matter of Epistemology, which looks at proof or evidence for existence of a Fact or General Principle.

• Proof of a fact can be known by sense observation.
  For Example: Rohit saw a red colored liquid.

- The proof of this can be known by perception of the liquid as red.
- If the liquid is actually red, then the fact is confirmed.

• Proof of a fact can also be provided by Deduction.
  For Example: Aseem has come to school today.

This fact can be proved by the following deduction.

P1: Aseem comes to school with a red bag
P2: The red bag is present today
Conclusion: Therefore Aseem is present today.

• Proof of a General Principle is given by Induction and Experimentation.

For Example:
Consider the General Principle : Water is an essential ingredient necessary for plant growth.

To prove this inductively, many plant that receive water need to be observed. If all of them grow well, then the general principle is ‘If there is water, Plants grow’ is held to be true.

But Induction is not sufficient. It is coupled with Experimentation. In experimentation, conditions are deliberately manipulated and their results are matched with expected outcome.

For Example:
In Experimentation, Some plant samples are collected. They are divided into two groups.
- One group is fed water; the other group is devoid of water.
- The result in Growth is observed in both cases.

If it shows that the Plant fetched with water grew well and those not fetched with water did not, confirms the General Principle that “If there is water, there is Plant growth”.

Asking for a justification of a statement always proceeds with a question. Like ‘How do we know that water leads to plant growth?’

Proof of a General principle follows a systematic, sequential order. The structure of this order is described in subject matter of Logic.