Portuguese to English Art/Literary Art, Arts & Crafts, Painting sculpture / public art / philosophy

Hi. This is in a text about the work of a sculptor. The paragraph that precedes this one discusses his upbringing in Italy, and the influence of classical art on his development. I'm really stuck on this phrase - I've toyed around with ideas such as 'aesthetic logic' 'material' 'rationale' etc etc. I'm aware that the concept of 'sensible reason' exists in philosophy, but I'm not sure the adjective 'sensible' would be very clear here. All thoughts much appreciated - it's the kind of phrase I come up against a lot as an art translator, but every now and then it seems particularly hard to translate!

'Formou assim um espírito plástico bebendo nos exemplos dos clássicos, que se tornaram seus paradigmas. Nas origens dessa consciência cultural, encontrou ainda os signos simbólicos para as metáforas da sua poética e uma razão sensível para as suas criações.
«Para mim o triângulo é a forma que simboliza a razão, o pensamento racional.[...]» (the text goes on to discuss the particular relevance of the triangle for him.

many thanks