Sāṃkhya Kārikā verse 5

prati-viṣaya-adhyavasāyaḥ dṛṣṭaṃ trividham-anumānam-ākhyātam |
tat-liṅga-liṅgi-pūrvakam-āpta-śrutiḥ āpta-vacanaṃ tu ||

prati - with regard toviṣaya - an object; any object of affection or concern or attentionadhyavasāya - mental effort, apprehension; determination to begin an activity with a view to get the fruitdṛṣṭa - seentrividha - three foldanumāna - inferenceākhyāta - said, told, declared, made knowntat - that, thisliṅga - manifest, sign, genderpūrva - precedingāpta - a credible or authoritative personśruti - hearing , listening; the ear, organ or power of hearing; that which is heard or perceived with the ear; sacred eternal sounds or words as heard by sages, differing from smṛti or what is only remembered and handed down in writing by authorsvacana - the act of speaking , utterance; statement, declarationtu - moreover

Commentaries and Reflections

Commentary by Paul Harvey:

Direct observation involves selective ascertainment through the senses.
Inference is of three kinds:
– The past shaping the future
– Projecting the whole from the part
– Forming a comparison from a similar.
Authentic authority is trusted words and teachings.”