LEVELS OF PRACTICAL KNOWLEDGE
The dispute among Thomists has centered around the relative roles of speculative and practical knowledge. Is practical knowledge independent or does it depend upon speculative knowledge? Unfortunately, the terms "speculative" and "practical" are often used without precision. What exactly does practical knowledge mean? The danger is that "practical reason" – or speculative reason, for that matter – might become a mantra, repeated for its salutary effect, with no clear thought as to what it means.
Jensen funda su clasificación del saber especulativo y práctico en e ST I, 14, 16:
Alguna ciencia es sólo especulativa, y alguna es sólo práctica; y alguna es en parte especulativa y en parte práctica. Para probarlo, hay que saber que alguna ciencia puede ser llamada especulativa de tres maneras. 1) Primero, por parte de lo conocido, en cuanto que no puede ser cambiado por el que lo conoce: es lo que sucede con la ciencia que el hombre tiene de lo natural o de lo divino. 2) Segundo, por el modo de conocer. Ejemplo: cuando un arquitecto analiza una casa definiendo, dividiendo y considerando los principios universales que le son aplicables. Esto es factible considerándolo especulativamente, no porque sea factible; pues factible es aquello a cuya materia se le aplica la forma; y no la reducción de los componentes a principios formales universales. 3) Tercero, por el fin. Pues, tal como se dice en el III De Anima: El entendimiento práctico se distingue del especulativo en el fin. Pues el entendimiento práctico está ordenado al fin de la acción; mientras que el entendimiento especulativo tiene por fin el encuentro de la verdad. Por eso, cuando un arquitecto piensa cómo puede ser construida una casa, no para construirla, sino para saberlo, con respecto al fin estará ante una consideración especulativa aun cuando sea factible.
Así, pues, la ciencia que analiza especulativamente lo conocido, es sólo especulativa. La que lo analiza según el modo o según el fin, en parte será especulativa y en parte práctica. Y cuando está ordenada al fin de la acción, será exclusivamente práctica.
We have, then, four levels, (i) The object known might be speculative; it is not the sort of thing that human beings order in their actions (como el sol o la luna). [2) The object known might be practical, such as an engine, but all that is known of it is speculative: what it is, how it functions, and so on. (3) The object and mode might be practical, as when someone knows how to make an engine. (4) The end of the agent himself might be practical, that is, he applies his knowledge to the activity; he actually builds engine.
TABLE 1-1. Types TABLE I-1. Types of Speculative and Practical Knowledge
Object
Knowledge
Object
Mode
End
Purely speculative
Non-operable
resolving
knowing
materially practical
operable
resolving
knowing
virtually practical
operable
composing
knowing
fully practical
operable
composing
doing
p. 106
We have seen that Aquinas thinks that the good is a final cause, and that we know this cause through its effect, which is desire or inclination. The character of this inclination is grasped through observations of where activities end. This line of thinking, when it applies to beavers or trees, is purely speculative. For human beings, it is speculative until the final step, in which the good is discovered and we have materially practical knowledge

204
The act of will is not merely some external addition; rather, the role of the knowledge itself changes. The role of fully practical knowledge is not simply to reflect the world; in addition, it is to be the form of our actions. Fully practical knowledge does not simply add force of will; rather, the knowledge itself has now become the form of the will

205
As the form of action (and not simply as a reflection of the world) reason is "true" insofar as it correctly forms the action. Even the poisoner’s judgment that he ought to give a double dose has a measure of this "truth," if indeed the double dose is needed to achieve the murder. The judgment correctly forms the act of murder. Ultimately, however, the judgment of the poisoner (expressed in the imperative "Give a double dose") lacks the complete practical truth of forming desire and action. Aristotle says that practical knowledge is true through comparison with right desire.1 Since the desire to murder is itself disordered, the judgment of the poisoner does not conform with right desire but with wrong desire. As such, his judgment is false.
Fully practical truth, then, has two requirements. First, it must reflect the way the world really is. Turning right at Louisiana Street must truly be the way that gets Louis to the opera. Second, it must conform with right desire. Given the ultimate end of his nature, it must be proper for Louis to go to the opera, rather than to the homeless shelter. Only by meeting these two requirements can Louis’s knowledge properly form his desire and action.

224 The will itself moves only consequent upon knowledge. Reason, then, precedes the will. Nevertheless, it does not precede the will as a moving force; it simply knows the good and thereby presents it to the Will. The movement in the will follows not on account of the nature of the knowledge; rather, it follows on account of the naturae of the will. By itself, the knowledge that something is a human good is just that. Knowledge. In relation to the will, however, it is knowledge – and presentation- of the proper object. This materially practical knowledge, then, does not move by efficient causality; it moves by a kind of final causality.
Practical knowledge, then, is practical precisely as derivative upon the will. Even when the will is absent we do call some knowledge practical, but we do so only because it shares some features with truly practical knowledge. Some knowledge, for instance, concerns the same sorts of things as does fully practical knowledge; we call this knowledge materially practical. In essence, however, it is simply knowledge. The fact that its object relates in a certain way to the will is incidental to the knowledge itself In itself, it is simply an awareness of some object in the world.

226
Ultimately, then, knowledge is practical through something extrinsic to it, namely, through an act of will. No knowledge is prescriptive by nature, apart from an act of will. No knowledge is categorically imperative by nature.

226
The first knowledge of the good, then, cannot depend upon the desire of the will, for the will presupposes the knowledge. Rather, the first knowledge depends upon nonconscious inclinations, the inclinations of the various powers and of the soul itself Reason first perceives a reality beyond itself and only then perceives its own action; it then perceives itself tending toward knowledge. Finally, reason perceives the good. It grasps the good of knowledge but it grasps it as a good of the person, which is the object of the will.
-------------------------


1 8, Nicomachean Ethics, book 6, chapter 2, II39a30.