This also could be called non-mantra meditation. For we don't force the mind to think a mantra but just let it think whatever it will. However, we have to observe or be aware that it is thinking. But since the mind can only do one thing at a time, either think or be aware, it must flip back and forth between the two states. It thinks, then it remembers or becomes aware that it is thinking; it thinks again, and again it becomes aware, and so on.
A common occurrence, especially for those just beginning to do meditation, is that the mind gets sucked into thinking, and is no longer aware that it is thinking. It begins to daydream, and perhaps even fall asleep. With practice, however, the mind's balance shifts the other way, from thinking to awareness; and it is possible for some that thinking stops altogether, and the mind reaches the state of no thought.
Passive meditation requires less concentration than active or mantra-directed meditation. For in passive meditation the mind is allowed to pick the subject and go with it, with only the requirement that it must stop on occasion to remember that it is thinking. At times, this won't be easy, stopping thinking to remember, because the mind is a powerful thinker, even an entertainer. It has the capability of generating or manifesting a spectrum of thoughts, recollections, images and plots, from the wonderful, sublime, loving and humorous to those not so wonderful, sublime, loving and humorous. Therefore, it can bring up strong emotions so much so that frequent breaks are needed to halt the show, and let the mind remember that it is only a show.
The breaks from thinking are breaks of awareness. In the break the mind forms the thought, "I am". "I am the mind" and "I am aware" that I have been thinking, but now "I am not thinking".
"I am": It is useful during the break to expand on that awareness, by adding a role to the "I am". Some examples are:
"I am breath" - The mind concentrates on breath and then resumes thinking.
"I am the watcher" - The mind remembers that thoughts come and thoughts go, and watches them arise and depart.
"I am with Jesus on a boat in a calm or troubled sea of thought" - The mind is at rest knowing that with Jesus the boat will always stay afloat.
"I am a worshipper of God" - The mind enters into his glorious majesty and awesomeness, the beauty of holiness. We bow down, or fall prostrate, before God, in our hearts, or in actuality, by bringing ourselves down to the floor. Hallelujah (Praise the Lord)!
"I am a child and/or servant of the God of awareness" - The mind recalls that God assumes roles of awareness, such as "I am almighty", "I am everlasting", "I am redeemer", "I am creator", "I am one", and "I am that I am", and recalls also that Jesus manifests many roles, such as, "I am the way", "I am truth", "I am life", "I am light", "I am salvation", "I am son of man", "I am resurrection", "I am the shepherd", "I am the vine" and "I am the word".
"I am becoming perfect" - The mind chooses which thought to embrace and rejoice with and which thought to not embrace and rejoice with. For the latter thoughts, the mind can either patiently watch them depart or interrupt them with a mantra thus ending passive meditation for a period.
One common thought to be aware of is the thought of dissatisfaction. For example, the mind may say: "This is not right"; or "I don't feel right"; or "I am not doing well"; "I'm not quite there"; "I'm uncomfortable"; "My life is not as it should be". The mind should watch such thought arise and watch them depart, reminding itself that, yes, I am not perfect, but I am on a journey with God toward perfection. I am becoming perfect.
Remember that life is precious, every moment is precious, every breath is precious, every thought is precious, every word is precious, and every deed is precious.
In Genesis 17:1 God said to Abraham, "Walk before me and be blameless (without blemish, perfect)". In Matthew 5:48 Jesus said, "You must be perfect as your heavenly Father is perfect".