Homo non ex necessitate eligit, quia quod possibile est non esse, non necesse est esse.
Man does not choose of necessity, because that which is possible not to be, is not of necessity.
Sententia sive iudicium rationis de rebus agendis est circa contingentia, quae a nobis fieri possunt, in quibus conclusiones non ex necessitate sequuntur ex principiis necessariis absoluta necessitate, sed necessariis solum ex conditione.
The formal aspect of decision or judgment is of what is to be done is about things that are contingent and possible to us. In such matters the conclusions do not follow of necessity from principles that are absolutely necessary, but from such as are so conditionally.
Quod autem possibile sit non eligere vel eligere, huius ratio ex duplici hominis potestate accipi potest. Potest enim homo velle et non velle, agere et non agere, potest etiam velle hoc aut illud, et agere hoc aut illud.
Now this formal aspect why it is possible not to choose, or to choose, may be gathered from a twofold power in man. For man can will and not will, act and not act; again, he can will this or that, and do this or that.
Cuius ratio ex ipsa virtute rationis accipitur. Quidquid enim ratio potest apprehendere ut bonum, in hoc voluntas tendere potest. Potest autem ratio apprehendere ut bonum non solum hoc quod est velle aut agere; sed hoc etiam quod est non velle et non agere.
The formal aspect of this is seated in the very power of aspectual apprehension of form. For the will can tend to whatever aspect is apprehended as good. Now formal aspect can apprehend as good, not only this, viz. "to will" or "to act," but also this, viz. "not to will" or "not to act."
Et rursum in omnibus particularibus bonis potest considerare rationem boni alicuius, et defectum alicuius boni, quod habet rationem mali, et secundum hoc, potest unumquodque huiusmodi bonorum apprehendere ut eligibile, vel fugibile.
Again, in all particular goods, it can consider an aspect of some good, and the lack of some good, which has the aspect of evil, and in this respect, it can apprehend any single one of such goods as to be chosen or to be avoided.
Solum autem perfectum bonum, quod est beatitudo, non potest ratio apprehendere sub ratione mali, aut alicuius defectus. Et ideo ex necessitate beatitudinem homo vult, nec potest velle non esse beatus, aut miser.
The perfect good alone, which is Happiness, is the formal aspect that cannot be apprehended under a formal aspect as an evil, or as lacking in any way. Consequently man wills Happiness of necessity, nor can he will not to be happy, or to be unhappy.
Electio autem, cum non sit de fine, sed de his quae sunt ad finem, ut iam dictum est, non est perfecti boni, quod est beatitudo, sed aliorum particularium bonorum. Et ideo homo non ex necessitate, sed libere eligit.
Now since choice is not of the end, but of the means, as stated above (q13 a3), it is not of the perfect good, which is Happiness, but of other particular goods. Therefore man chooses not of necessity, but freely.