The Kuzari discusses the religious claims of Yishmael (Islam) and implicitly contrasts them with Persia (Zoroastrianism), framing Yishmael's descendants as those who claim proximity to Avraham's legacy while Persia represents an entirely foreign religious civilization.
(ד) אָמַר הַכּוּזָרִי: וְאֵיזֶה דָבָר שֶׁהוּא נוֹטֶה מִן הָאֱמֶת אֵצֶל הַפִּילוֹסוֹפִים גָּדוֹל מֵאֱמוּנָתָם שֶׁהָעוֹלָם חָדָשׁ, וְשֶׁהוּא נִבְרָא בְשֵׁשֶׁת יָמִים, וְשֶׁהַסִּבָּה הָרִאשׁוֹנָה מְדַבֶּרֶת עִם אֶחָד מִבְּנֵי אָדָם, עִם הָרוֹמְמוּת שֶׁמְּרוֹמְמִים אוֹתוֹ הַפִּילוֹסוֹפִים מִידִיעַת הַחֶלְקִיּוֹת. וְעִם זֶה הָיָה רָאוּי כְּפִי מַעֲשֵׂה הַפִּילוֹסוֹפִים וְחָכְמָתָם וַאֲמִתָּתָם וְהִשְׁתַּדְּלוּתָם, שֶׁתִּהְיֶה הַנְּבוּאָה יְדוּעָה בָהֶם וְנִמְצֵאת בֵּינֵיהֶם, מִפְּנֵי הִדָּבְקָם בָּרוֹחֲנִיּוֹת, וְשֶׁיְּסֻפַּר עֲלֵיהֶם נִפְלָאוֹת וְנוֹרָאוֹת וְכָבוֹד וּגְדֻלָּה. וַאֲנַחְנוּ רוֹאִים הַחֲלוֹמוֹת הַנֶּאֱמָנִים לְמִי שֶׁלֹּא הִתְעַסֵּק בְּחָכְמָה וְלֹא בְּזִכּוּךְ נַפְשׁוֹ, וְנִמְצָא הֵפֶךְ זֶה בְּמִי שֶׁטָּרַח בָּהּ. וְזֶה מוֹרֶה כִּי יֵשׁ לַדָּבָר הָאֱלֹהִי וְלַנְּפָשׁוֹת סוֹד אַחֵר זוּלַת מַה שֶּׁזָּכַרְתָּ, אַתָּה הַפִּילוֹסוֹף:
Al Khazari: What could be more erroneous, in the opinion of the philosophers, than the belief that the world was created in six days, or that the Prime Cause spoke with mortals, not to mention the philosophic doctrine, which declares the former to be above knowing details. In addition to this one might expect the gift of prophecy quite common among philosophers, considering their deeds, their knowledge, their researches after truth, their exertions, and their close connection with all things spiritual, also that wonders, miracles, and extraordinary things would be reported of them. Yet we find that true visions are granted to persons who do not devote themselves to study or to the purification of their souls, whereas the opposite is the case with those who strive after these things. This proves that the divine influence as well as the souls have a secret which is not identical with what you say, O Philosopher.