Early in 359 he dispatched to them the Liber de Synodis. It is a double letter, addressed to Western bishops, but containing passages intended for Orientals, into whose hands the letter would doubtless come in time. Hilary had recognized that the orthodox of the West had kept aloof from the orthodox of the East, firstly from ignorance of events, secondly from misunderstanding of the word ὁμοούσιος, and thirdly from the feelings of distrust then prevalent. These facts determined the contents of his letter.