Today the image I saw was of some steam rising so I automatically looked for the boiling water from which it emanated. Though I couldn't see the water I knew it must have been there. We cannot see one gaseous particle of steam but with a concentration of the seemingly transparent and colourless steam particles we actually can identify the mass of it. Similarly, though we can't see God in the natural (in this steam analogy we have water as the natural product) we can see spiritual evidence of Him, such as with perfect timings of events beyond our control and planning, obvious coincidences etc. Let's not dismiss these important occurences. Our inner being longs to fill a gap which we can't necessarily explain. When we build up this spiritual evidence we start to recognise and believe in God's existence. He will reveal Himself to you. "Ask, and it will be given you; seek, and you will find; knock, and it will be opened to you". (Matthew 7:7).
