there is no structure is sensation. What kind of thing is this so-called structure? Attaching a name, a universal and so forth. According to Dignāga our mind always takes raw sense data or particulars and interprets them or groups them together in more complex ways, compares them to past experiences, gives them names to classify them based on general attributes (samanyalaksana) and so forth. This process he terms kalpana (arranging, structuring). This cognitive process is already different from sensation, which is a simple cognition based only on the immediately present. Thus pratyakṣa is only awareness of particular sense data such as a patch of green color and the sensation of hardness, never awareness of a macroscopic object such an apple which is always a higher level synthesis. For Dignāga, sensation is also inerrant, it cannot "stray" because it is the most basic and simple phenomenon of experience or as he puts it: "it is impossible too for the object of awareness itself to be errant, for errancy is only the content of misinterpretation by the mind." Also, for Dignaga, pratyakṣa is mostly phenomenalist and is not dependent on the existence of an external world. It is also inexpressible and private. Anumāṇa Anumāṇa (inference or reasoning) for Dignāga is a type of cognition which is only aware of general attributes, and is constructed out of simpler sensations. Inference can also be communicated through linguistic conventions. A central issue which concerned Dignāga was the interpretation of signs (linga) or the evidence (hetu) which led one to an inference about states of affairs; such as how smoke can lead one to infer that there is a fire. This topic of svārthānumāna (reasoning, literally "inference for oneself") is the subject of chapter two of the Pramāṇa-samuccaya while the topic of the third chapter is about demonstration (parārthānumāna, literally "inference for others"), that is, how one communicates one's inferences through proper argument. According to Richard Hayes, in Dignāga's system, to obtain knowledge that a property (the "inferable property", sadhya) is inherent in a "subject of inference" (paksa) it must be derived through an inferential sign (linga). For this to occur, the following must be true: The inferential sign must be a property of the subject of the inference. That is, there exists in the subject of inference a property, which is different from the inferable property and which is furthermore evident to the person drawing