Know Yourself
If you read Kath-Upnishad, you'll find one beautiful analogy which clears your idea about soul, intellect, mind, body and senses. So, here's the analogy. There is a chariot going on a path towards its destination. Owner of that chariot is sitting inside the chariot. Charioteer is controlling the horses with bridle. Now here, the owner of chariot is Soul, the charioteer is intellect, the bridle is mind, horses are senses, the chariot is body, the path is life and the destination is moksha. Here, owner of chariot which is soul whose destination is Moksha is actually idle. He can't give command or can't control horses. Charioteer, the intellect can control horses, senses with bridle, the mind. Without proper control, horses don't follow path and the chariot will not reach to its destination. So, if intellect can't use mind properly, mind can't control those senses and if senses are not in control, the soul can't reach at its destination.