The Purgative way is the beginning, or childhood stage of the spiritual life. It is the stage appropriate for those who have turned from a life of pursuing their own way and their own exaltation and who have determined to surrender their lives to the Lord to glorify and serve Him only. One enters the Purgative Way be being 'awakened' or 'born again.'
The appropriate practice of a beginning in the spiritual life is that of meditation, which is to say reading and reflecting upon the written word of God at increasing levels of spiritual depth. When we are alientated from God our minds are fallen and we consequently spend our time thinking about how to gratify the desires of the sinful nature [Ro 13:14 ]. When our spirits are reborn, our minds remain unchanged, except that they have the potential to be illuminated by divine truth, because now the Spirit is able to teach us the truth which our natural minds alone could not comprehend [1 Cor 2:14]. This is the point where Paul admonishes the believers in Philippi to think about whatever is pure, noble, etc. [Php 4:8], and the believers in Colosse to set their minds on things above rather than on the things of this world or on how to gratify their flesh [Col 3:1-2]
The basic effects of this process are that you are gradually drawn to some degree out of the kingdom of darkness into the kingdom of light. For example, you have taken your mind which was once fixed on the things of the world and set it on heavenly things - the Bible, the work of the Kingdom, etc. You have also been drawn away to some degree from the things of this earth and you have started to enjoy the presence of God and the work of the Kingdom. This is a process in which you are very active. However, there comes a time when you must learn a new way of walking with the Lord, because this process in and of itself is not sufficient to accomplish God's full intent for you - to be transformed in the image of His son.
The written word can tell you what is right and wrong, it can inform you as to the details about Jesus' life and teachings, but it can't make you holy. It can't give you power to overcome the world, the flesh, or the devil. In fact, it can't even enable you to really understand God or even His written word properly, because even though we are now thinking about spiritual things instead of worldly things, we are doing it with minds that are fallen and still partially in darkness. Your mind was born separated from God and it was trained to think according to the ways of the flesh, and it simply is not equipped to grasp the deep truths of God; that is why the Lord told Isaiah that His ways and His thoughts are as far above ours as the heavens are above the earth. The unfortunate thing is that there is nothing we, personally, can do about this situation. Adding more information won't change our condition, because once we have absorbed the written word, it's not the facts which we reason about that are fallen, it's the very mind that we use to reason about them.
The New Testament is replete with admonitions to be transformed by the renewing of our minds [Rom 12:2], to let ourselves be renewed in the knowledge of the Creator [Col 3:10], etc. The key to this transformation is given in 2 Cor 3:18:
In other words, when we actually behold the glory of Jesus, the Spirit literally transforms us so that we become like Him. This is an act which the early church referred to as contemplation. It is very distinct from meditation, in that it is not an intellectual exercise; it is an act of the heart and of the will - setting our hearts on things above [Col 3:1]. It is also fairly mysterious because we're never told why it is that spiritually beholding the glory of the Lord effects such a radical transformation in our innermost being.
Few people make the transition from meditation to contemplation directly. In order to effect this transition, it is often necessary for the Lord to lead us into a phase of passive purgation, an experience referred to commonly as the Dark Night of the Senses.