The occurrence of [greek]logikhn[/greek] (feminine of [greek]logikoV[/greek]) in 1 Peter 2:2: is explained in this comment:
Originally posted by johnnybanano
The proper understanding in this context of the adjective [greek]logikoV[/greek], a word derived from [greek]logoV[/greek] and hence normally pertaining either to reason or speech (“word”), is difficult to determine. It occurs only one other time in the NT (Romans 12:1), where the same ambiguity adheres.
If the root [greek]logoV[/greek] is to be understood in the sense of “reason,” then the meaning would be something that corresponds “reasonably,” that is, appropriately to the present situation: a “milk” whose content is appropriate to the Christian’s situation. Since it is a “milk” that leads to growth to salvation, it points to the spiritual rather than the material dimension of reality, and hence could also be translated “spiritual.” Some have argued for this meaning not in terms of conforming to reason but in opposition to corporeal milk, or as describing the purpose of God and his word which is true nourishment for Christians, but such arguments depart from any relation to the root meanings of [greek]logikoV[/greek].
If the root [greek]logoV[/greek] is to be understood in the sense of “word,” then [greek]logikoV[/greek] would express the relationship of [greek]gala[/greek] (“milk”) to the word of God as the proper nourishment for Christians. This understanding is supported by the use of [greek]logoV qeou[/greek] in 1:23 and is reinforced by the use of [greek]rhma[/greek] (= “word”) in 1:25a for the word of the Lord and 1:25b for the gospel. Since therefore, in this context, the word of God ([greek]logoV qeou[/greek]) was the agency by which the readers were rebegotten as Christians (1:23), and since the word of the Lord ([greek]rhma kuriou[/greek]) was the good news that has been communicated to them (1:25b), some relationship between the divine word and the adjective [greek]logikoV[/greek] seems most likely. It would, furthermore, be appropriate for Christians who were rebegotten by the word of God to yearn for that word so they may experience further growth leading to salvation. — Paul J. Achtemeier, 1 Peter (Hermeneia), pages 146-47; Fortress Press, 1996.