A friend of mine posed a series of questions for a metaphysical discussion group we both frequent. I was not able to attend that night, but I thought the questions were good and worth thinking on.
Is there a veil between worlds? How much? If not a veil, are there other separations?
To the first question, “Is there a veil between the worlds?”:
The conception of a veil separating this world from the world of spirits in general is not something I ascribe to any more. I certainly think there are times when our perception of the various Worlds is more open, and sometimes this has to due with worldview or mindset, and other times to do with significant events, such as holy days, anniversaries of deaths, astrological events, and other times where spiritual potential for contact is elevated.
It also depends on which ‘worlds’ you are talking about. I think there could well be worlds out there that could be shielded from contact, worlds we may never visit because our minds can’t grasp the place to be able to, worlds so openly hostile to our presence that our spirit is repelled or put at risk, or worlds that we have to have an express invitation to see in the first place. Not so much a general veil as the question asks.
To the second question: “How much?”
A way to think about this would be in terms of effort. Some spirit worlds are completely intertwined with our own, eg Gods whose forms/names/Beings are more immanent, landvaettir, the Dead, and Ancestors. I have a graveyard a stone’s throw away from my house. I can walk to it when traffic is low. I have good relationships with the Dead of this graveyard as these Dead are close and were willing to forge good relationships with me.
Gods whose forms/names/Being are more transcendent, vaettir more distant physically and spiritually from us, Ancestors further back in our bloodline or separated across an ocean would all be examples of Beings who may be harder to contact. Going with the previous example, visiting some the other Dead I have relationships with means I have to drive to get to other graveyards, and sometimes these visits turn more into day trips. There isn’t a veil here, but there is more effort expended to do the physical journey to visit the world of that graveyard.
To the last question: “If not a veil, are there other separations?”
Some spiritual worlds may take more out of us or present us with more challenges that we need to prepare for when we go to visit them. As with the previous example it requires more preparation and better weather for me to visit a graveyard farther away from me than the one nearest me. I’ve visited my home graveyard in the midst of Winter with most of the graveyard being a snow-covered ice sheet. I would not make this kind of trip for a graveyard even a bit further away unless I needed to.
Applying this idea of effort, preparation, and work to get places is part of it. Spiritual worlds are inhabited and it can be seen as rude to outright invasion to try to get into a world you are not formally invited into. Trying to break into Helheim is a fool’s errand. It’s river, Gjöll, has a bridge, Gjallarbrú, to Helheim’s gate which is guarded by Móðguðr and Garm, Hela’s wolf. Asgard has a mighty wall to block anyone uninvited from coming into its walls and defenders on them. Even if a given spiritual world does not have these kinds of defenses, it makes sense to ask to come in rather than barge in. You are likely to have better reception and the relationship begins on a good note.
Turning this around, this is also why warding is so important. If you do not ward then any old spirit that strolls by can walk into your proverbial front door. In a sense you are protecting your ‘world’ from those Beings you don’t want strolling through. It also helps with discernment because if you have good wards you have a safe place free from the energetic and spiritual intrusions of the world around you where you can relax and live, and invite the Beings you will into a far more well-ordered space than if everything was just open.
Sarenth Odinsson 
Veiling between worlds was introduced to me as a Celtic concept. That at certain times, the veils between worlds are thin.
Romans don’t think in those terms. We have the opening of the Mundus, the Well to the Underworld, which happens three times a year. Certain times of the year such as February and May, the lemures, manes, and other spirits are more active. However, generally, we live in a spirit haunted world, where wards are necessary for home and family life.
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Morgan Daimler has a great post about the veil between this world/the Otherworld- apparently it has its origins in Spiritualism & Theosophy, and some of the Celtic Twilight era authors like W.B. Yeats drew on those ideas so they’ve influenced much of generic Wheel of the Year Paganism.
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