ratiocination
Concise Oxford English Dictionary © 2008 Oxford University Press:
ratiocination /ˌratɪɒsɪˈneɪʃ(ə)n, ˌraʃɪ-/
▶noun formal the forming of judgements by a process of logic; reasoning.
– derivatives
ratiocinate verb,
ratiocinative adjective,
ratiocinator noun.
ratiocinate verb,
ratiocinative adjective,
ratiocinator noun.
– origin C16: from L. ratiocinatio(n-), from ratiocinari ‘deliberate, calculate’, from ratio (see ratio).
'ratiocination' also found in these Oxford entries:

