Meditation

Meditation is an unbroken uninterrupted or incessant flow of the idea of the object that is concentrated upon.  If you close your eyes when you do Trataka and mentally visualise the picture of the object of Trataka, it is concrete meditation or Saguna meditation.  Concrete meditation on an object is necessary for an untrained mind, in the beginning. If you meditate on an abstract idea, it will constitute Nirguna meditation.

For beginners whose minds are engrossed in and filled with passions and impurities, meditation on a form is absolutely necessary.  A Murty or any concrete form such as a Pratima is indispensable during meditation.  Without undergoing a course of concrete meditation in the beginning, especially for the ordinary type of people, it is absolutely impossible to start Nirguna meditation at the very outset.

The vast majority of aspirants commit a serious mistake in jumping to Nirguna meditation all at once. They will only break their legs.  The mind is so framed as it demands a form to cling to.  Meditation on a Murty, i.e., a stone-image remains the stone as it is, but the devotion of the devotee goes to the Lord.  He is pleased.  Divine Grace will surely descend.

You will have to superimpose the attributes of God on the stone-image.  You will have to imagine that there is the Antaratman hidden in the image, the all-pervading, indwelling presence, the pure consciousness, the Chaitanya at the back of it.