Parallel Lives
To understand parallel lives, we need to understand the mechanism of human cognition and manifestation of the world.
Everything in the world manifests in the form of vibrations, waves and frequencies.
We know that our world is what we perceive through our senses. This way our world is made of vision, sound, smell, taste and tactile vibrations.
The sense organs are capable to receive vibrations that fall under a specific range or frequencies e.g. our eyes can only see the Violet rays only between the wavelength of 380–450 nm and frequency of 680–790 THz.
The same way, each sense organ has its own capacity constraints.
We are not able to perceive anything beyond faculties of our senses even when there could be other vibrations existing :
We know that our TV set projects only the channel it is tuned to even when there are signals of other channels, too.
The concept of Parallel Universe is based on the notion that there are other dimensions of the world where things manifest in different type and range of vibrations and frequencies. Because those vibrations are beyond the capacity of our sense organs, we never perceive them and do not believe them to be real.
According to the spiritual philosophy of life, with a view to have comprehensive experience, the spirit consciousness explores the world in different forms with different sets of cognitive abilities. This is like our use of night-vision cameras to be able to capture images in the dark.
The physical form of this spirit is what we normally experience as our being. Thru the physical body and the senses, the spirit experiences the gross world.
The subtle form of the spirit operates in subtle vibrations and experience the world beyond physical.
Thus, the spirit manifests in different dimensions and in different bodies in the same dimension, simultaneously. This, in a way optimizes the exploration endeavor. This simultaneous manifestation of spirit is called Parallel Lives.
As an individual, even when our consciousness is operating on various other dimensions, we don’t know about it because our cognition is constrained by the inbuilt sense organs.
Thus, it is possible that your consciousness may be leading more than one lives simultaneously e.g., one entity is manifesting as a Christian to experience what does it feel like living a life through christian beliefs and values and another entity as a scientist exploring the world without any religious philosophy.
As the phenomena of soul experiencing in different lives in different time period involves past lives, the phenomena of experiencing multiple things in the same linear time period involves parallel lives.
This is one way of understanding it and there could be many more concepts to prove it or even to reject it outright.