In order to understand the Law of Attraction, there are a few things that need to be laid as foundation of understanding.
Firstly, the label that we use here as Source Energy has not much difference than that of which many people have use the label of God - which depicts the unseen forces that has always been there. But we will not use the label of God here simply because the intentionality of this word has been intepreted differently by various sectors of religion and also people.
There are so many similar words that associated with this Source Energy - Consciousness, Universe, All-That-Is, Pure Positive Energy, Love, God and etc. All of them mean the same the essence of our intention to describe this unseen forces.
Imagine there is this bunch of energy flowing out from a source. This bunch of energy is formless and omnipresent. This energy consists of data which can be also be assumed as intention.
Same Energy but Different Intention.
So when this energy is perceived by the perceiver using its sensory perception, it has gain its form and from there this energy is intepreted into something meaningful to the perceiver.
For example, this same energy projecting into different intention as a Human, an Elephant, a Tree, a Rock and Water. Thus, when the perceiver (let's say human beings) perceives via one of the sensory perception of "sight" of this energy of a big clump with long tube, it begins to see the form which is labeled as Elephant. This same goes to the Tree, Rock and Water.
The energy in the Water is no difference than the energy of the Tree. The energy of the Tree is no difference than the energy that is flowing in the Human. It is the intentionality of the energy which differentiate the form but they are all from the same essence - the Source Energy.
So, in this huge and limitless Universe, this Source Energy keeps expanding and becoming everything. And when this "everything" are able to be perceived, they give some meaning to the perceiver. When they are not able to be perceived (for example, the energy cannot be seen, heard, touched, smelled or tasted), it does not mean that the energy does not exist. It simple means that the energy has a different intentionality that can be perceived by other different forms (other than human beings).
