The following sutta addresses the interesting concept of 'papanca'
MN 18 - Madhupindika Sutta
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In his text "Concept and Reality", venerable Nanananda defines papanca as "conceptual proliferation" and this has increasingly become the accepted translation of the term, although in the translation above, Thanissaro Bhikkhu translates it as "complication".
If we watch the so-called 'monkey mind', we see that it really does leap around when uncontrolled and unsettled. The mind 'conceptually proliferates' and we find ourselves prone to becoming lost in thought. Right Mindfulness is helpful in countering papanca.
Metta,(Sanskrit prapañca): In doctrinal usage, it signifies the expansion, differentiation, 'diffuseness' or 'manifoldness' of the world; and it may also refer to the 'phenomenal world' in general, and to the mental attitude of 'worldliness'. In A. IV, 173, it is said: "As far as the field of sixfold sense-impression extends, so far reaches the world of diffuseness (or the phenomenal world; papañcassa gati); as far as the world of diffuseness extends, so far extends the field of sixfold sense-impression. Through the complete fading away and cessation of the field of sixfold sense-impression, there comes about the cessation and the coming-to-rest of the world of diffuseness (papañca-nirodho papañca-vupasamo)." The opposite term nippapañca is a name for Nibbāna (S. LIII), in the sense of 'freedom from samsaric diffuseness'. - Dhp. 254: "Mankind delights in the diffuseness of the world, the Perfect Ones are free from such diffuseness" (papañcābhiratā pajā, nippapañca tathāgatā). - The 8th of the 'thoughts of a great man' (mahā-purisa-vitakka; A. VIII, 30) has: "This Dhamma is for one who delights in non-diffuseness (the unworldly, Nibbāna); it is not for him who delights in worldliness (papañca)." - For the psychological sense of 'differentiation', see M. 18 (Madhupindika Sutta): "Whatever man conceives (vitakketi) that he differentiates (papañceti); and what he differentiates, by reason thereof ideas and considerations of differentiation (papañca-saññā-sankhā) arise in him." On this text and the term papañca, see Dr. Kurt Schmidt in German Buddhist Writers (WHEEL 74/75) p. 61ff. - See D. 21 (Sakka's Quest; WHEEL 10, p.
In the commentaries, we often find a threefold classification tanhā-, ditthi-, māna-papañca, which probably means the world's diffuseness created hy craving, false views and conceit. - See M. 123; A. IV, 173; A. VI, 14, Sn. 530, 874, 916.
Ñānananda Bhikkhu, in Concept and Reality: An Essay on Papañca and Papañca-saññā-sankhā (Kandy 1971, Buddhist Publication Society), suggests that the term refers to man's "tendency towards proliferation in the realm of concepts" and proposes a rendering by "conceptual proliferation," which appears convincing in psychological context, e.g. in two of the texts quoted above, A. IV, 173 and M. 18. - The threefold classification of papañca, by way of craving, false views and conceit, is explained by the author as three aspects, or instances, of the foremost of delusive conceptualisations, the ego-concept.