Either - Deism
Deism is the assumption of a single, overall, unifying - but
potentially abstract and impersonal - source of order and meaning for reality.
therefore refers to the assumption of some kind of Deity; but this is not the same as theism. Theism refers more
specifically to the reality of gods or God. (Therefore, all Theists are Deists; but not all Deists are Theists.)
Deity might not be any kind of god; but instead be assumed to be something abstract; some kind of principle, tendency, process, or ultimate structure.
Deism implies a coherent universe, a coherent reality.
Or - Not-Deism
Not-Deism implies that there is no coherent basis to reality; reality just-is - it could have been otherwise, and it could become otherwise.
Because there is assumed to be no Deity, there is no reason why things should stay as they are
Strictly, nothing can be explained in terms of 'why' it is as it is, because there is no overall order to relate it to - but explanation can only proceed in terms of describing (or theorising about) how something came to be, historically (and contingently - it could have been otherwise).
When I was an atheist theoretical biologist I was looking to explain biological phenomena in one of two ways. Either as a consequence of adaptive selection across multiple generations - or else the assumption that there was no relevant explanation: things were 'accidental'.
The assumption was that most biological phenomena had no explanation in terms of natural selection. For example, bones are white because they are made of chemicals such as calcium phosphate that just happens to be white - and blood gets its colour from haemoglobin that just happens to be red; but the colour of bones and blood has no biological explanation - it is an accident.
A few biological phenomena - such as the mammalian eye - were 'explained' in theoretical terms as a consequence of a sequence of purposeless genetic mutations that incrementally led to the progressive elaboration of - probably - transparent skin above light sensitive neural tissue, a recessed pit for this light sensitive tissue (to provide directional information), a transparent lens to focus the light... and so forth.
Each stage was a consequence of purposeless mutations which led to undirected body changes that were preserved and amplified because they increased differential reproductive success. But there was no overall purpose to the changes, there was no meaning to the existence of the mammalian eye except that is what just happened to have been the outcome of what happened in the past - there was no guarantee that the eye would not be changed or lost in future generations.
And these negatives are a consequence of the fact that modern biology assumes there is no Deity and therefore there is no planned, directed, created, organised cohesion to reality.
For Not-Deism the ultimate reality is that stuff happens, or does not happen. Indeed, for Not-Deism there is nothing to suggest that stuff really- does happen - because everything we 'know' we 'think', and thinking is itself a consequence of unorganised accidental processes - unplanned, undirected and so on...
Any apparent organisation anywhere is only apparent - we have no way of knowing that there really is organisation because we have already assumed (by Not-Deism) that there is no ultimate organisation in reality.
For Deism, by contrast, assumes that there is some kind of organisation, cohesion, order to reality. From my perspective as a biologists, I noticed that many mathematicians and theoretical physicists expressed Deistic views: for example that mathematics was universally and necessarily true, and the organizing principle of reality.
As a Non-Deist biologist I regarded this as a residual superstition, or a pretentiousness to which mathamatical people were prone - the conceit that their own special aptitude gave them privileged access to reality and therefore unique prestige.
My own views were that mathematics was a closed system of tautologies, nothing really meant anything, and the universe was (probably) chaos - a mixture of apparent randomness caused by some kind of deep determinism - or perhaps apparent determinism caused by deep randomness... we had no real way of knowing.
Just stuff-happening and probably changing (but who knows?), on-and-on, with no point or purpose. That was the consequence of my assumption of Not-Deism.