Meditation is defined as, maintaining a steady flow of thought on the same object. Typically, इश्वर isvara or saguna सगुण brahma ब्रह्मन्, the Lord with attributes, is the object of such a flow of thought. You can maintain that flow by repeating a name in your mind, by focusing your attention on a form, by thinking about the glories ‘of the Lord, by performing mental worship etc. Meditation includes all these different processes. It is called upasana उपासना or mental worship of the Lord. In this, there is a duality between the devotee and the Lord, between the one who is meditating and the Lord who is meditated upon.
There are many kinds of meditation, but we define meditation as maintaining a thought-flow centered upon the Lord. It requires some support in the form of a word, a mantra, of an image to keep the mind focused. It is not emptying the mind of thought, or thoughtlessness. The yoga-sastra योगशास्त्र defines meditation as the stoppage of thoughts or a complete stilling of the mind. If there is identification with the thoughts, there is bondage. The purpose of stilling the mind is to dissociate it from all thought so that there is no bondage. When there are no thoughts there is no identification and in the absence of identification, there is only the self. The idea in the yoga-sastra is that we can gain the knowledge of one’s own. self only if we still the mind. However, rather than emptying the mind, we prefer mental worship, which invokes the devotee in the person who meditates. This helps to purify the mind and secure the grace of God.
Another form of meditation is contemplation upon the realities of life or upon the nature of one’s own self; it can be called the reality; meditation. This meditation is of the nature of f seeing’ rather than worshipping. In mental worship, some kind of visualization may be involved, but here we see, for example, the order that obtains in the universe. There can be meditation upon your own self where you see the self as consciousness, or you can contemplate on the reality -seeing the reality as it is. You can meditate upon acceptance, compassion or the order. You can choose a topic and contemplate on it.
When meditation involves the worship of God, it is soothing, healing, and purifying for the mind. It is desirable that इश्वर isvara be involved in the meditation. Ideally, meditation should involve a spirit of worship. The Upanisads suggest that we meditate upon pranava प्रणव or om ॐ and superimpose isvara on om. The repetition, of om then becomes meditation. If one reflects upon brahman with the help of om, it becomes contemplation. Thus, one worships om as isvara in the first instance and sees the self as om or isvara in the second.
In the उपनिषद Upanisads, we find उपासना upasanas that are meditations upon the Lord with attributes, and they are done with the help of certain models prescribed in the texts. For example, we find meditations upon the harmony and oneness obtaining in the universe, based on various elements of nature or the luminaries of the different worlds. In one meditation, the universe, which is the manifestation of isvara, is looked upon as the cosmic person with the sun for his eyes, with fire as his mouth, and so on. Seeing the cosmos as a person, as one organic whole, becomes meditation. These are some kinds of meditations that are taught in the Upanisads.