Plato’s most famous discussions of form involved things like the form of virtue, of justice, or of the Good. These are questions that perplex the wise and the sincere inquirer. They therefore could not be the objects of any simple dogma.
In Aristotle there is a deep connection between form and ends. For both Aristotle and Plato, “essence” is never merely factual but always has what analytic philosophers call a normative dimension. It is not the kind of thing that could be simply given (see Form, Substance).
Brandom says that for Kant and Hegel, concepts always have a normative dimension, and intentionality is to be explained in terms of normativity rather than vice versa.
The necessity in formal logic and mathematics also has a normative character, but it is different from the previous examples in that it is univocal and definitely knowable. Things that are “formal” in this modern sense are quite different from form for Plato or Aristotle, which is closer to what Brandom would call conceptual content (see Mutation of Meaning). Well-founded certainty is only possible in domains that are purely formal in the modern sense.
Anything involving the “real world” involves interpretation, which is never finished. In life we work, act, and love on the basis of partial interpretations of the forms of things.