Your thoughts are basically concerned with the mind–body problem.
Your principles:
1. Reality is an environment, where the mind operates.
Reality is the sum or aggregate of all that is real or existent within the universe, as opposed to that which is only imaginary, nonexistent or nonactual.
But the mind can operate on the grounds of, or take account of imaginary, nonexistent or nonactual facts. So we must "enlarge" this concept of reality in order for this principle to be accurate. You could use a definition like Anaximander's first principle, Aristotle's unmoved mover, Stoic's pneuma, or TAO.
2. Because we are conscious, we must exist.
Consciousness, at its simplest, is awareness of internal and external existence.
I suppose that for every conscious being (having awareness of), self-existence is self-evident by definition.
3. If we exist, there must be at least one cause for our existence.
Causality is an influence by which one event, process, state, or object (a cause) contributes to the production of another event, process, state, or object (an effect) where the cause is partly responsible for the effect, and the effect is partly dependent on the cause.
Here, things start to get really complicated. Although - for some - causality may appear to be a rather straightforward concept, it is not. Nearly all philosophers - in one way or another - have a differentiated view of causality. As a food for though I recommend to read this. I also recommend my answer to another post. What I want to say - in simple words - is that what you seem to think of as an external thing (the cause), may in fact be an internal disposition towards life itself; so that "must" may be the effect of being in the intellectual level.
4. If we exist and there is a cause for our existence, there is a substrate on which the mind exists and operates and laws govern the
mind.
Since you talk about laws - in the context of a substrate - I assume you are talking about physical laws; and not philosophical principles. Here you are making the assumptions a) that [the] causality [of existence] operates and/or is inherent in a substrate, that is basically physical and b) that the mind is enclosed or limited to this substrate. And although I could cope with a) (but as a manifestation and not as an inherent property), b) is in fact the mind–body problem.
5. From the above I propose that the reality in I operate is the same as the one that governs the mind.
This is basically principle 4, phrased with different words. So, summing up, I do not see that this conclusion follows. My view is that the mind cannot be reduced to a specific (objective) substrate; it operates in many levels, encompassing many realities; it's a subjective journey longing to find The objective.
