Exegesis:

epignous (5.30; 6.33, 54) ‘perceiving,’ ‘recognizing.’ Some think that the preposition epi ‘upon’ has what is called the perfective force, and that the verb would therefore mean ‘to know thoroughly,’ ‘to be fully aware.’ J. A. Robinson, however, has convincingly demonstrated that the verb denotes knowledge reached by directing attention epi ‘upon,’ ‘toward’ a particular person or object. Moulton & Milligan quote examples from the papyri which bear out this sense.

tō pneumati autou ‘in his spirit,’ i.e. ‘in himself’ (not ‘in his (Holy) Spirit’). Taylor calls this phrase the ‘dative of sphere’; Manson and Translator’s New Testament translate ‘by his spirit.’

pneuma ‘spirit’: this is the third meaning given the word in Mark (cf. 1.8 and reff. for ‘Holy Spirit’; 1.23 and reff. for ‘unclean spirit’). The meaning here (and in 8.12 and 14.38) is, as Arndt & Gingrich define it, “the source and seat of insight, feeling, and will, generally as the representative part of the inner life of man.” In 14.38 it is opposed to the outer life, the physical.

ti ‘why?’: Black takes this to be another example of a rhetorical question, expressing dismayed surprise (cf. previous verse).

Translation:

It is often difficult to use for spirit in this verse the same term which may be employed for Holy Spirit, and it is especially important to avoid a word for spirit which will imply a demon or a familiar spirit. That is to say, one must not give the impression that Jesus was using a familiar spirit to ferret out the thoughts of the scribes (the technique ascribed often to mediums) or that he had some magic power to send out his spirit to pry into the thought of others (a not infrequent idea of the activity of shaman). On the other hand, this spirit was not the Holy Spirit, but the spirit of Jesus as a focus of intellectual activity and discernment. The equivalent of this aspect of personality is, however, in many other languages spoken of as distinct from any word for spirit. For example, in South Bolivian Quechua, Southern Bobo Madaré, and Chol one must use ‘heart’ and in Conob one must employ a term which identifies the ‘viscera.’

In some languages one cannot ‘question within oneself,’ for the word ‘to question’ means to ask another. Hence, in this verse, as well as verse 6, one must use a verb such as ‘to think’ or ‘to wonder’ (Amganad Ifugao).

Because of the shift in subjects, i.e. Jesus as the subject of the perceiving and the scribes as the subject of the questioning, it is often advisable to break the sentence and to begin the latter half as a new sentence, e.g. ‘he said to them…’ (Shilluk).

Quoted with permission from Bratcher, Robert G. and Nida, Eugene A. A Handbook on the Gospel of Mark. (UBS Handbook Series). New York: UBS, 1961. For this and other handbooks for translators see here .