To live by the Spirit is to take the Spirit—the realization of the resurrected Christ—as our person (Gal. 2:20a). To live by the Spirit equals to have Christ living in us and equals taking the Spirit as our person.
To live may mean to have life, but to walk means to have our being. The Greek words translated "walk" in Galatians 5:16 and 25 are two different words. They signify the two aspects of the Christian walk.
The first word, used in Galatians 5:16a, denotes the general walk in our daily life, implying a common, habitual daily walk. This walk is referred to also in Romans 6:4; 8:4; and Philippians 3:17-18. The walk in all these verses is the general walk in our daily life.
The second word for walk, used in Galatians 5:25, refers to a walk according to rules, that is, the walk in line, in an orderly, regulated manner (Gal. 6:16; Acts 21:24; Rom. 4:12; Phil. 3:16), referring to a walk that takes God's unique goal as the direction and purpose of the Christian life, by living in the new creation (Gal. 6:15-16), by pursuing Christ (Phil. 3:12, 16), and by practicing the church life (Rom. 12:1-5; Eph. 4:1-16), so that God's economy for the church may be fulfilled.
The first kind of walk is the daily walk for our daily living, and the second is a walk according to rules for the church. The church is our goal, and the church is also our purpose. We walk this way and we take this way as a rule because our human life has a goal and a purpose, and this goal and this purpose are to have the church life. The Christian life has two aspects. One aspect is the Christian daily life, the normal, habitual, common living in our daily life, with no particular goal or purpose in view. But we Christians should not be simply for our daily life. We Christians must be persons for the church. The church is God's goal, and the church is God's purpose. Because of this, we must have rules to regulate our walk. The three main rules for the second kind of walk are to live in the new creation, to pursue Christ, and to practice the church life, so that God's economy for the church may be fulfilled.