Yukti is known as reasoning in Hindu philosophy. Science is based upon reasoning. Art and religion also make use of yukti. Yukti alone cannot be used everywhere for proof or for solving a problem. But reasoning is absolutely necessary for understanding any subject in a logical and scientific manner.
One should always consider advice that is based on yukti, which means expedient, suitable and reasonable. There is an adage in Sanskrit which states that (yukti yuktam vacho grahyam) a fit and suitable statement should be accepted or received. However, reasoning alone cannot be proof of a shastra. Proof through words (sabda pramana) is another way which Hindu philosophies engage in teaching (upadesha) Vedas, which constitute the base for almost all Hindu philosophical texts. Although they are not totally dependent on reasoning, they do constitute a part of knowledge.
Reasoning is used as a means and not as an end in itself. Reasoning favorable to Vedas is called suyukti. Yukti is the base of any science, but using it for bandying words without a logical base invariably results in sorrow.
The first quarter of the second chapter of Brahma Sutras is meant to discuss the opposites of reasoning. The entire work of Badarayana Brahma Sutras is based upon this Yuktivada. A study of this would make one an expert in yukti (reasoning) which is based upon experience and understanding. This is common to all philosophies and shastras. It is also called Chit-Shakti or power of intellect. An individual with reasoning power is called a rationalist, upapanna, one who is an expert in arguing. Yukti is considered a part of logic (Tarka Shastra).