5:14 of full age. “Of full age” is literally “of mature maturity,” essentially the same as “perfection” (Hebrews 6:1).
5:14 senses. “Senses” here means “esthetic senses” (Greek aistheterion), used only this once in the New Testament. It implies a sort of spiritual intuition, by which the sensitive Christian can more or less automatically discern whether something is right or wrong. However, this sense is developed only by attaining real maturity in the Scriptures.