Another point to be noted in connection with the main metaphysical theories of Patañjali is the Sphoṭa theory which considers the relation of words with their ideas and the things which they signify. Generally these three are not differentiated one from the other, and we are not accustomed to distinguish them from one another. Though distinct yet they are often identified or taken in one act of thought, by a sort of illusion. The nature of this illusory process comes to our view when we consider the process of auditory perception of words. Thus if we follow the _Bhāshya_ as explained by Vijñāna Bhikshu we find that by an effect of our organs of speech, the letters are pronounced. This vocal sound is produced in the mouth of the speaker from which place the sound moves in aerial waves until it reaches the ear drum of the hearer, by coming in contact with which it produces the audible sound called dhvani (_Yoga-vārttika_, III. 17). The special modifications of this dhvani are seen to be generated in the form of letters (_varṇa_) and the general name for these modifications is nāda. This sound as it exists in the stage of varṇas or letters is also called varṇa. If we apply the word śabda or sound in the most general sense, then we can say that this is the second stage of sound moving towards word-cognition, the first stage being that of its utterance in the mouth of the speaker. The third stage of śabda is that in which the letters, for example, g, au, and ḥ, of the word “gauḥ” are taken together and the complete word-form “gauḥ” comes before our view. The comprehension of this complete word-form is an attribute of the mind and not of the sense of hearing. For the sense of hearing senses the letter-forms of the sound one by one as the particular letters are pronounced by the speaker and as they approach the ear one by one in air-waves. But each letter-form sound vanishes as it is generated, for the sense of hearing has no power to hold them together and comprehend the letter-forms as forming a complete word-form. The ideation of this complete word-form in the mind is called sphoṭa. It differs from the letter-form in this that it is a complete, inseparable, and unified whole, devoid of any past, and thus is quite unlike the letter-forms which die the next moment after they originate. According to the system of Patañjali as explained by the commentators, all significance belongs to this sphoṭa-form and never to the letters pronounced or heard. Letters when they are pronounced and heard in a particular order serve to give rise to such complete ideational word-images which possess some denotation and connotation of meaning and are thus called “sphoṭas,” or that which illuminates. These are essentially different in nature from the sounds in letter-forms generated in the senses of hearing which are momentary and evanescent and can never be brought together to form one whole, have no meaning, and have the sense of hearing as their seat.