Write a short note on the concept of knowledge of Vaibhashik Buddhist school.

The Vaibhashika is one of the early schools of Buddhist philosophy, and its concept of knowledge revolves around a realist perspective on perception and external objects. In the Vaibhashika tradition, knowledge is primarily understood through the lens of direct perception (pratyaksha) and inference (anumana).

1. Direct Perception (Pratyaksha):
   Vaibhashikas assert that direct perception is a reliable means of knowledge. Perception is considered as the immediate and non-conceptual awareness of external objects. They believe that the objects of perception have real existence, independent of the perceiver.

2. Inference (Anumana):
   In addition to direct perception, inference plays a crucial role in the Vaibhashika epistemology. Inference is a process of arriving at knowledge about unseen or unperceived phenomena based on the observation of associated or concomitant factors.

3. Three Modes of Valid Cognition (Pramana):
   Vaibhashika acknowledges three pramanas or valid means of knowledge: perception, inference, and testimony (aptavacana). Testimony refers to the reliable communication of knowledge by a trustworthy source.

4. Reality of External Objects:
   Vaibhashikas maintain a realist stance by asserting the objective existence of external objects. They argue that entities, such as atoms (paramanu), possess inherent existence and are not mere conceptual constructs.

While the Vaibhashika school emphasizes the reality of external phenomena and the reliability of perception and inference, it is important to note that later Buddhist schools, especially the Sautrantika and Yogachara, presented contrasting views on the nature of reality and the role of conceptualization in the process of knowledge.