Responsa for Shabbat 299:7
רמי ליה רב אחא בר רב הונא לרבא מי אמר ר' יוחנן דיבור אסור הרהור מותר אלמא הרהור לאו כדיבור דמי והאמר רבה בר בר חנה אמר רבי יוחנן בכל מקום מותר להרהר חוץ מבית המרחץ ומבית הכסא שאני התם דבעינן (דברים כג, טו) והיה מחניך קדוש וליכא
[explicit] speech is forbidden, but thought is permitted.<span class="x" onmousemove="('comment',' A hint is not explicit but left to the understanding. ');"><sup>12</sup></span> R. Aha son of R. Huna pointed out a contradiction to Raba. Did R. Johanan say: Speech is forbidden, thought is permitted, which shows that thought is not the same as speech? But surely Rabbah b. Bar Hanah said in R. Johanan's name: One may meditate [on learning] everywhere, except at the baths or in a privy? There it is different, because [the fulfilment of] and thy camp shall be holy<span class="x" onmousemove="('comment',' Deut. XXIII, 15. ');"><sup>13</sup></span>
Teshuvot Maharam
A. The decision of the teacher is incorrect, for ordinarily whatever a Jew is not allowed to do on the Sabbath, he is not permitted to tell a Gentile to do.
This Responsum is addressed to R. Nathan, an uncle of R. Meir. But according to Cr. 20, it was sent to R. Hezekiah of Merseburg.
SOURCES: Cr. 20; Pr. 637; Wertheimer 15; Mord. Shabb. 314; Hag. Maim., Shabbat 6, 9.