There are three things–knowledge, detachment, and devotion. Knowledge is like a boat; some boat is capable of crossing the ocean of this world, and some boat is incapable. If you don’t have a boat, then you will drown. Of course, a capable person can swim across the ocean and doesn’t need a boat. Both most people will need a boat. Knowledge is that boat. The boat that will help you cross the ocean is spiritual knowledge. And the boat that will break down in the middle of the ocean is material knowledge. You can make some technology with material knowledge, but you cannot solve the problems of life. Therefore, getting the correct boat is very important, but not enough.
If this boat is tied to the shore, then you cannot cross the ocean, even if you have the boat. Therefore, we have to cut the attachment to this world, which is like cutting the rope that ties the boat to the shore. For example, by Vedic knowledge, we can create some material technology, but doing that would be just like tying the boat to the shore. So those people who are using Vedic knowledge to create material technology are using the boat to stay afloat in water, but not cross the ocean. Their boat is tied to the shore, so all their efforts are ultimately a wastage of time. Detachment means trying to understand that the boat is meant to cross the ocean, not just to keep you afloat.
Then after you have a boat, and the rope to the shore has been cut, you have to row the boat. That rowing of the boat is the application of knowledge and is called devotion. All practice is a devotional practice. In devotion, there is knowledge, and there is detachment. That devotion requires serving God by whatever ability we have. There are three kinds of service: by our words, by our mind, and by our body. By the words means chanting the names of God. By the body means engaging our wealth, property, material resources, etc., in the service of God. By the mind means that the service is mindful, not doing something for the sake of it. When our words, body, and mind are engaged in the service of God, then the process is called devotion. This spiritual process is rowing the boat.
There are many ways in which knowledge, detachment, and devotion are presented in Vedic texts, but the basic principle is not changed. So, if a person tries for knowledge alone, then he may get a boat, but it remains tied to the shore, and even if some spiritual practice is performed, but the rope is not cut by detachment, then it is just like rowing a boat that is tied to the shore. It has no effect. Likewise, if someone gets a boat, but doesn’t practice devotion, that is just like a boat used to stay afloat rather than cross the ocean. Therefore, all each of the three principles are necessary.
When all three are performed collectively, then each one reinforces the other. Thus, as you cut the rope of attachment, the boat becomes stronger. If you row the boat correctly, the boat becomes stronger. If all the three are not happening simultaneously, then something is wrong. Either the boat is tied to the shore, or there is no rowing of the boat, or the boat is material knowledge.