I simply want to know what the Rambam thinks about ghosts, spirits, demons, and things like that.
כָּל מַה שֶּׁבָּרָא הַקָּדוֹשׁ בָּרוּךְ הוּא בְּעוֹלָמוֹ נֶחְלָק לִשְׁלֹשָׁה חֲלָקִים. מֵהֶן בְּרוּאִים שֶׁהֵן מְחֻבָּרִים מִגּלֶם וְצוּרָה וְהֵם הוִֹים וְנִפְסָדִים תָּמִיד כְּמוֹ גּוּפוֹת הָאָדָם וְהַבְּהֵמָה וְהַצְּמָחִים וְהַמַּתָּכוֹת. וּמֵהֶן בְּרוּאִים שֶׁהֵן מְחֻבָּרִים מִגּלֶם וְצוּרָה אֲבָל אֵינָן מִשְׁתַּנִּין מִגּוּף לְגוּף וּמִצּוּרָה לְצוּרָה כְּמוֹ הָרִאשׁוֹנִים אֶלָּא צוּרָתָן קְבוּעָה לְעוֹלָם בְּגָלְמָם וְאֵינָן מִשְׁתַּנִּין כְּמוֹ אֵלּוּ. וְהֵם הַגַּלְגַּלִּים וְהַכּוֹכָבִים שֶׁבָּהֶן. וְאֵין גָּלְמָם כִּשְׁאָר גְּלָמִים וְלֹא צוּרָתָם כִּשְׁאָר צוּרוֹת. וּמֵהֶן בְּרוּאִים צוּרָה בְּלֹא גּלֶם כְּלָל וְהֵם הַמַּלְאָכִים. שֶׁהַמַּלְאָכִים אֵינָם גּוּף וּגְוִיָּה אֶלָּא צוּרוֹת נִפְרָדוֹת זוֹ מִזּוֹ:
Everything which the Holy One, blessed be He, created within His world is divided into three categories. They include: a) Creations which are a combination of matter and form. They are constantly coming into existence and ceasing to exist; for example, the bodies of man and beasts, plants, and metals.b) Creations which are [also] a combination of matter and form, but do not change from body to body and from form to form as those in the first category. Rather, their form is permanently fixed in their matter, and they do not change as the others do; for example, the spheres and the stars [which revolve] in them. The matter [from which] they [are composed] differs from [a simple conception of] matter, and their form differs from [a simple conception of] form. c) Creations which have form, but no matter at all; for example, the angels, for the angels do not possess bodies or corporeal being, but rather are forms which are separate from each other.
וּמַהוּ זֶה שֶׁהַנְּבִיאִים אוֹמְרִים שֶׁרָאוּ הַמַּלְאָךְ אֵשׁ וּבַעַל כְּנָפַיִם. הַכּל בְּמַרְאֵה הַנְּבוּאָה וְדֶרֶךְ חִידָה. לוֹמַר שֶׁאֵינוֹ גּוּף וְאֵינוֹ כָּבֵד כַּגּוּפוֹת הַכְּבֵדִים. כְּמוֹ שֶׁנֶּאֱמַר (דברים ד-כד) "כִּי ה' אֱלֹהֶיךָ אֵשׁ אֹכְלָה הוּא" וְאֵינוֹ אֵשׁ אֶלָּא מָשָׁל. וּכְמוֹ שֶׁנֶּאֱמַר (תהילים קד-ד) "עשֶֹׁה מַלְאָכָיו רוּחוֹת":
What is meant by the prophets' statements that they saw an angel of fire or with wings? All these are prophetic visions and parables, as [Deuteronomy 4:24] states: "God, your Lord, is consuming fire," though He is not fire and [the description of Him in this manner] is only metaphoric. Similarly, [Psalms 104:4] states: "He makes His angels as winds....
So I don't see ghosts and demons in the first part. Their existence is not present in the list.
There is a relatively famous Rambam (Moreh Nevuchim) who says sheidim (demons) don't exist, which seems to contradict numerous gemaras.
Rav Hutner's explanation of this anomaly is that sheidim are the imaginings of the world.
Imaginings are not real unless you're talking about them.
So, are your imaginings real? No.
But if you ask a psychologist if the imaginings that caused his patient to commit suicide were real, he will say yes.
So sheidim do not exist, but the gemara can still talk about them.