The Illuminative Way is the second distinct stage in the spiritual life corresponding to a state of spiritual adolescence. It is referred to as "illuminative" because your spirit begins to be bathed in a divine, spiritual light or revelation which is received often through the practice of contemplation. This is the place where God begins to reveal Himself to you directly and supernaturally deliver you from those sins which you previously were required to struggle against or flee from. You also start receiving divine understanding and insight into the scriptures and the spiritual realm. Phenomenon such as words of knowledge, words of wisdom, and prophetic utterance are common manifestations in this stage of the spiritual life. There are a host of other experiences which are often part of the Illuminative Way - visions, raptures, etc. - which are beyond the scope of this discussion. (Click here for a more extensive (but still incomplete) treatment of some of these experiences.) It's basically a way of life in God where the Holy Spirit begins to teach you directly instead of using an intermediary like the Bible or a human teacher. It is the beginning of the fulfillment of Jer 31:34 where God indicates that we will be taught by Him, rather than by one another. There are similar passages in the New Testament in 1 Jn 2:27 and 2 Pet 1:3-4. Tersa de Avila says that when you are in this place God can teach you in an instant things which would take you years to understand by yourself.
Now this is not to say that you do not need a firm grounding in the written word; it simply means that once you have built the foundation, you have to build on it. The way you build on it is by letting God teach you directly about who He is. It's also a place where you need to be especially discerning of spiritual counterfeits and where you really need accountability to other believers and to the word so that you don't get sucked off into some side-track somewhere and stop growing. The way to progress in and benefit from the illuminative life is to have your will so firmly fixed on loving the Lord that you will not be willing to settle for anything less than Him. There is a temptation when God starts giving you spiritual revelation or prophetic knowledge to become fixated on that particular gift and lose your focus on the Lord. The mystics refer to this as becoming overly fixated on spiritual consolations. And the enemy will strongly encourage this because he will do anything to stop you from attaining the state of Divine Union which lies on the other side of the illuminative life.
An important thing to remember is that where earlier you could advance by your own effort, once you reach this place, you advance purely by the grace of God. The other thing is that the key to everything here is love. Julian of Norwich, an English mystic from the fourteenth century, wrote at great length about the love of God and that love being the central issue of spiritual revelation. God reveals Himself to you because He loves you; the things He reveals to you are basically to show you more of His love, and the reason why He shows them to you is to make you love Him more. If you receive a revelation of the Lord and fail to have your heart drawn out in love to Him as a result, because you're so exciting about getting a word of knowledge, or whatever, you have basically missed the point of the exercise. If you've heard the prophetic words coming forth these days where God says that He wants us to be looking at His face rather than His hand, you'll understand the importance that God places on having our hearts set on Him for Himself alone.
What gradually happens as you respond to these revelations is that you become so overwhelmed by His love that it weans you off of everything in the world which once captured your affections. Frankly, when you've begin to see and experience the love of God, there's just nothing in the world which can keep your attention for very long! And so as you continue surrender to God and let Him reveal His love for you, you become separated from the things of the world - not in a religious, Pharisaical sense, but in an interior, spiritual fulfilment of the command to love the Lord with all your heart, mind, soul, and strength.
The Illuminative Way was a very common experience in the early church, and it's starting to become common again. If you have been baptized with the Holy Spirit, God has basically invited you into this way of walking with Him. What's been happening for about the last hundred, starting with the Pentacostal outpouring and accelerating in the Charismatic renewal is that God has suddenly begun drawing people into this deeper place of walking with Him so that He can reveal more of His love to them. Since 1992 we have been witnessing the phenomenon of entire congregations being profoundly swept up in supernatural revelations of the love of God.
These kinds of experiences, however, are merely a foretaste of the complete union of the soul with God which is found in the Unitive Way - also referred to as a state of Spiritual Marriage. Between the Illuminative Way and the Unitive Way, however, is found another transition referred to as the Dark Night of the Soul.