  I will discuss mainly the definition of the ‘pervasion’ relation. First, however, a brief note on how the causal model of knowledge is applied to inference. The ‘special’ instrumental cause (karaṇa) of an inferential cognition is said to be the inferrer’s knowledge of the relevant pervasion relation. The ‘operative condition’ (vyāpāra) is said to be an awareness that the locus of inference (p) possesses such an inferential sign (h) as is pervaded by the property inferred (s). This is, in effect, an awareness which combines the two premises of the argument together immediately prior to the conclusion being derived, and is called the ‘parāmarśa’ or ‘consideration’. The ‘guṇa’ or ‘causal factor responsible for the truth’ of the inferential cognition is the condition that this ‘consideration’ be true, i.e. that the locus does in fact possess such a sign as is pervaded by the inferred property. Another auxiliary causal factor is that the inferrer must either not yet already know the conclusion or else must have a particular desire to infer (i.e. given, knowledge of the premises, the inference would normally take place mechanically, but if the conclusion is already known e.g. perceptually, then the inferrer has to have a special wish to re-establish it inferentially). This condition is known as ‘pakṣaṭā’, and should not to be confused with ‘pakṣadharmatā’, which is the name of condition (i) above.