The Collaborative International Dictionary
Rationalistically
Rationalistic \Ra`tion*al*is"tic\ (r[a^]sh"[u^]n*al*[i^]s"t[i^]k), Rationalistical \Ra`tion*al*is"tic*al\ (-t[i^]*kal), a. Belonging to, or in accordance with, the principles of rationalism. -- Ra`tion*al*is"tic*al*ly, adv.
Wiktionary
rationalistically
adv. In a rationalistic manner; in the context of rationalism