By "essential" I don't mean "necessary" or "required", I mean "of or pertaining to essences". What I'm calling "essential thinking" seems to me to be a form of
magical thinking, although it doesn't exactly fit into the linked-to definition. I'd say it's roughly related to sympathetic magic and the "law" of contagion.
If you're thinking about someone creating a magic potion to make a person fly, what are some likely ingredients? I think most of us will immediately think of things like feathers and bat wings -- bits of things that fly. Even a very rational person, who knows such potions are pure fantasy, can get into this magical mindset. The idea behind such potion ingredients is that there's some sort of "essence of flying" with which flying things are imbued. The complications of how something like a feather helps a bird to fly (and why they don't help, say, ostriches fly), consideration of how flight is an emergent phenomena of feathers, muscles, motor control, aerodynamics, all interacting in a very specific way, are conveniently swept away by reducing flight to an essence.
Essential thinking isn't necessarily wrong. If you think of heat as an essence (e.g. "caloric"), for example, even before having a deeper understanding of heat as molecular vibration or electromagnetic radiation, you can use that idea to come up with some rudimentary understanding of the flow of heat energy. Newton's gravitation was an essence, an invisible force that Newton could describe -- with a useful mathematical precision -- but that he could not explain.
Without the introduction of the equation F=GMm/r² Newton's gravitation would have been a far less compelling idea. In fact, gravitation would be little more than a tautology: objects are drawn together because there's a force that draws things together.
As pointless as that kind of tautology seems, however, when we run into things we don't fully understand people often find satisfaction in such tautologies, they even fancy such tautologies to be insightful -- so long as the tautology is obscured by enough excess verbiage. Why are things alive? Because they are imbued with life (élan vital). What is consciousness? The state of being imbued with consciousness.
Thinking of life and consciousness as essences doesn't really get us much of anywhere. The "law" of contagion roughly applies: all life and consciousness we know of is connected to other life, has grown out of and touched other living and conscious entities. An essential view of life hardly accounts for all of the complicated twists and turns of life and death and reproduction, however, or the interaction of living matter and non-living matter. You'll end up creating modern biology and making the notion of a "life essence" irrelevant by time you construct a sufficiently useful and predictive set of rules for how a hypothetical life essence would behave. Similarly, an essential view of consciousness fails to bring any useful value to understanding what we know about animal and human intelligence, psychology, neurochemistry, or the effects of brain injuries.
I think there's really only one major way that thinking of life and consciousness an essences (or one essence for both) is helpful, which is probably why the idea persists in the face of the much better emergent phenomena explanation: hope for immortality.
If life and consciousness are "just" emergent phenomena, one has to face how those phenomena can irrevocably cease when the complex, situational dance of chemicals and electrical charges is disrupted. If you cling to the idea of essences, however, one can imagine those essences as persisting separately from the merely material components of our existences, surviving death, persisting to live on in some other way or form.
In the essential view, an object like a rock or the whole universe might be said to be alive and/or conscious simply by imagining that they are "imbued" with a vital or conscious "essence". The rock and the universe don't have to act like anything we consider alive or conscious -- we can simply imagine that our hypothetical "essences" can fill or permeate these things without having the same effects seen when they are imbued into ferns and wombats and DU posters.
In New Age parlance, the much-abused word "energy" takes the place of the pre-scientific notion of an "essence". It's really just the same thing, however, except when the word "energy" is misused this way, the misuser hopes that scientific concepts like conservation of energy get to go along for the ride.
But since an essential view of life and consciousness doesn't add one bit to our understanding of living and conscious things, since an essential view doesn't have any testable consequences to differentiate from the far more testable and successful emergent phenomena explanation for life and consciousness, what's left here for an essential view other than wishful thinking, or ignorance, misunderstanding, and denial of the known science?