Which school is historically associated with the self-description “people of justice and oneness”?

The Four Proofs: Fiqh, Uṣūl al-Fiqh and Kalām

• Muʿtazilah
• The Ashʿarī school as its communal designation
• The Māturīdī school as its defining self-label
• The hadith scholars as a formal theological title