philosophies
That is the correct spelling of the plural of philosophy, which is "philosophies."
The correct plural form is "Doctors of Philosophy."
The plural form of vita is vitae.
The plural of responsibility is responsibilities.
The plural form of the noun thesis is theses. It is the standard plural form for a word of Greek origin ending in -is.
The plural form of him, her, or it is them. (objective pronouns)
Italy does not have a plural form.
As you say, it is doctors of philosophy, or in abbreviated form, PhD's.
The plural form of quiz is quizzes.
The plural form of beauty is beauties.
The plural form is spelt : subpoenas.
The plural form of radius is radii.
Trout is plural
The plural of foot is feet
The plural of dish is dishes.
That is the correct spelling of the plural of philosophy, which is "philosophies."
The plural form for the noun index is indexes.