dicenda sunt aliqua

Post tractatum de incarnatione Verbi, quod est origo et fons omnis doni gratuiti, dicenda sunt aliqua de gratia Spiritus sancti, quae nobis quadrupliciter consideranda occurrit.

This is the first sentence of Part V of Bonaventure's Breviloquium. Can the words in bold be translated as let us speak to some extent? If so, why is dicenda sunt plural?



Thanks.