By reason alone one cannot understand bhakti. Sri Rupa writes, svalpapi rucir eva syad bhakti-tattvavabodhika. It is reason combined with taste (ruci) that enables one to engage in sastra-yukti, to reason well as to the implications of sastra. Sri Jiva comments, “… logic along with full taste for the topic of bhakti can give an understanding of it.”
And as stated by Sri Jiva in his Sarva-samvadjini (citing Purusottama-tantra), it is sastra-yukti that is the supreme pramana, not merely sastra unto itself, or sastra in the hands of one without full taste for bhakti.
Sastra-yukti is a characteristic of uttama adhikari Vaisnavas. While the term “uttama adhikari,” as used by Sri Rupa, refers to the most eligible to engage in sadhana bhakti, Jiva Goswami’s understanding of sastra-yukti requiring “full taste for bhakti” appears to refer to the svarupa laksana or principal characteristic of the stage of bhakti within sadhana-bhakti known as ruci. And the ruci bhakta is certainly most qualified to engage in sadhana bhakti.