If we want to overcome the impoverished state of liturgical discourse, which results from focusing on only two categories (validity and licitness) and arrive at a fuller, more accurate picture, we must also consider fittingness and authenticity/legitimacy, which are two other irreducibly distinct perfections of liturgy.
A lecture given at Queen of Peace Parish in Patton, Pennsylvania, on September 21, 2020.
Video here:
https://www.youtube.com/watch?v=esmjGfT24Ew
The full text, including a chart, may be found here:
https://rorate-caeli.blogspot.com/2020/11/the-four-qualities-of-liturgy-validity.html
or here:
http://www.newliturgicalmovement.org/2020/11/the-four-qualities-of-liturgy-validity.html
On the Four Qualities of the Liturgy: Validity, Licitness, Fittingness, and Authenticity