Why is the attribution of some works to Giotto disputed?

The attribution of works to Giotto remains problematic and speculative because few of his works are documented and little is known about his life. Scholars often face challenges due to the following factors:1

• Lack of Documentation: Because primary records are scarce, researchers must rely on later literary traditions, which are sometimes inconsistent or contradictory.12
• Stylistic Discrepancies: Many works, such as the St. Francis cycle in Assisi, exhibit stylistic differences when compared to universally accepted masterpieces like the Arena Chapel frescoes. This leads some experts to attribute such works to an unknown "Master of the St. Francis legend" rather than Giotto himself.3
• School Pieces vs. Original Hands: Some works bearing Giotto’s signature or trademark are often viewed by critics as "school pieces" produced by his workshop, whereas unsigned, undocumented works—like the Ognissanti Madonna—are sometimes accepted as being entirely by his own hand due to their superior quality.4
• Restoration and Alteration: Works like the Navicella mosaic are difficult to evaluate because they were significantly altered in later centuries, leaving only fragments of the original work for analysis.4