Genitive Adjective with no Noun Referent

Question

Praejudicium autem cum dico, non volo intelligi qualecunque praegressum judicium in animo; quasi animus ab omni omnino judicio liber esse debeat: sed judicium quod semel formatum tanti fit, ut eo quis stare velit, atque idcirco rationes omnes respuere quae isti labefactando idoneae sunt.

How would "tanti" be translated in this sentence? Also, how is my overall translation?

But when I say prejudice, I do not want all preceding judgment whatsoever to be understood: as if the mind should be absolutely free from every judgment, but at least from a formed judgment made of such, that someone desires to remain therein, and on that account rejects all reasons which are apt to undermine it.

Answer 1

Other than the phrase in question, your translation is excellent. Tanti is a so-called "genitive of indefinite value", see Allen and Greenough section 417. This is a use of adjectives expressing quantity in the context of a verb whose meaning can assign or assess value, as here fit: literally, "it (the judgment) becomes / is made of such value that...".

Note also that semel means "once". So the phrase in question can be translated "a judgment which, once formed, becomes of such great value", or less literally, "so important / weighty that...".