In this way the Lord especially stressed reference to authoritative scriptures. In other words, one should not whimsically accept a person as an incarnation but should try to understand the characteristics of an incarnation by referring to the scriptures. An incarnation of the Supreme Lord never declares Himself to be an incarnation, but His followers must ascertain who is an incarnation and who is a pretender by referring to authoritative scriptures.
Any intelligent person can understand the characteristics of a real incarnation by understanding two kinds of features—the principal features, called personal characteristics, and the marginal features, comprising His activities. The scriptures describe both kinds of features. For example, in the beginning of Śrīmad-Bhāgavatam (1.1.1), the features of an incarnation are nicely described. In that verse, the two terms param (supreme) and satyam (truth) are used, and Lord Caitanya indicated that these words reveal Kṛṣṇa's principal feature.