This argument-as-bridge won't carry any weight. For example, if the big bang is the first motion and the start of time, what would "then trigger" the big bang?

Instead of making a raft of claims, perhaps the OP would take it one at a time. Start with,"there must have been a first motion in the universe." Why must there have been? Granted its logical sense is appealing, but it's the universe you're attempting to describe, and while I personally believe that it - the universe - makes sense, I don't believe I have the sense to make sense of it.

This argument-as-bridge won't carry any weight. For example, if the big bang is the first motion and the start of time, what would "then trigger" the big bang? — tim wood

The start of time could be coincidental withe the end of time, with the big bang triggered by the big crunch. The big crunch after all is the only place in the universe to get enough matter/energy for the big bang.

Start with,"there must have been a first motion in the universe." Why must there have been? — tim wood

I'm using an axiom equivalent to 'material ordered collections have a first member'. I think it's a self evident axiom. The collection of negative integers is not a valid counter example as it is not fully defined so can't exist in the material world (in our minds only).

The start of time could be coincidental withe the end of time, — Devans99

Sounds good. What did you say time is?

I don't see how the universe can impose the speed of light speed (=time/distance) unless there is something real about time. Time having a start would reenforce the argument that time is real. Believing that time is real and being a finitist means I believe time has an end too. If each moment needs another moment before it, then circular time is the only allowable configuration.

1. There must have been a first motion in the universe; no first motion implies no motion at all in the universe which makes no sense. — Devans99

Either there was a first motion or the universe extends infinitely back in time.

2. There cannot be a stretch of infinite length time before the first motion as what would then trigger the first motion? — Devans99

There can't be any time at all prior to a first motion. Time is motion/change.

3. The only alternative to the infinite length of time before the first motion is a start of time. — Devans99

That premise we agree on.

4. IE there must be a start of time. — Devans99

No, because of my comment re the first premise.

The start of time could be coincidental withe the end of time, with the big bang triggered by the big crunch. The big crunch after all is the only place in the universe to get enough matter/energy for the big bang. — Devans99

I'm not at all fond of talk that has more than one universe. I wouldn't say that a big crunch is the end of one universe and a big bang the start of another. I'd just call it one universe that has undergone a (or that regularly undergoes periodic) big crunch(es) and big bang(s).

Time is not change; time governs change through the speed of light (speed=distance/time) law.

Do you agree with the axiom 'material ordered collections have a first member'? If yes then you should agree with my argument and time has a start follows.

I'm not at all fond of talk that has more than one universe. — Terrapin Station

There is just one universe, just one big bang and one big crunch. No need for multiple universe, it's the same universe in an eternal circle of time.

Time is not change — Devans99

I wasn't asking what you thought, so that I might simply adopt your view.

In my ontology/metaphysics, time is simply change/motion. Could someone convince me to change my ontology? Perhaps. But that certainly wouldn't be easy. I didn't just pick my view out of a hat (and not just a moment ago).

Do you agree with the axiom 'material ordered collections have a first member'? — Devans99

I have no idea. I'm not entirely sure what it's referring to. What is the source of that axiom? I don't recall encountering that before. (Maybe I did and I just don't recall it . . . I'd have to review it.) Just for general info, I don't at all buy realism for sets or for mathematics/mathematical objects in general. Sets are something we make up.

There is just one universe, just one big bang and one big crunch. No need for multiple universe, it's the same universe in an eternal circle of time. — Devans99

Well, then time wouldn't have a beginning.

The axiom 'material ordered collections have a first member' I made up. Combined with another axiom ‘motion exists’, this gives the first point in my argument that there must be a first motion. You disagree with the reasoning?

Well, then time wouldn't have a beginning — Terrapin Station

The beginning/end point on a circle is arbitrary. The Big Bang / Big Crunch seems like the most natural choice.

The axiom 'material ordered collections have a first member' I made up. Combined with another axiom ‘motion exists’, this gives the first point in my argument that there must be a first motion. You disagree with the reasoning? — Devans99

I'd agree that stipulatively, material ordered collections can have a "first member." I don't know what such a stipulation is supposed to have to do with objective ontology, though. Or how it would argue agaisnt the notion that time might extend back infinitely.

All I'm saying is that if you agree with the axiom, then you agree there must have been a first motion. It argues against time extending back indefinitely as follows:

What was the cause of the first motion? There must of been a cause, and time extending back indefinitely before the first motion contain no cause. So time can't extend back indefinitely; there must be a start of time.

All I'm saying is that if you agree with the axiom, then you agree there must have been a first motion. — Devans99

All I agree with is that we can stipulate that. It's like saying, "You must write the word 'there' with a 'z' in the middle instead of an 'e,' like this: 'thzre'"

I think it's a good axiom. The only logical alternatives to the 'material ordered collections have a first member' axiom are:

1. 'material ordered collections do not a first member'
2. 'material ordered collections sometimes a first member'

1 is easy to dismiss with reference to real life examples. For instance, a stamp collection has a first member.

2 is equivalent to 'there exists a material ordered collection with no first member'. This is a strange thing to belief in IMO. Certainly there are no examples of such from nature.

All I'm saying is that if you agree with the axiom, — Devans99

And just here is the problem. Accept this, and that follows - no argument; maybe not even worth arguing. But the road from a logical model to reality requires observation. Absent the observation, you can't get theah from heahh.

But the road from a logical model to reality requires observation — tim wood

The question of whether there was a start of time or not may be unanswerable by observation. We are at least 14 billion years too late to observe any start of time. Unless we invent time travel, a metaphysical answer to the question maybe the only answer we will ever get.