Why God cannot have many forms: male (Shiv शिव), female (Shakti शक्ति), dark blue (Ram राम), golden (Sita सीता), diminutive (Vaman वामन), glorious (Ganesh गणेष), cheerful (Vishnu विष्णु), meditative (Brahma ब्रह्मा), majestic (Krishna कृष्ण), or all forms combined (Durga दुर्गा)?