Your argument suffers from a major deficiency which I invite you to remedy.
What definition of 'truth' are you using here? What test will tell us whether a statement is true or not, do you say?
(My own definition is that a statement is true to the extent that it corresponds with / conforms to / accurately reflects objective reality. You obviously disagree, so what do you say instead?)
The problem with this is that objective reality is apparently subjective.
For example...
Can we objectively tell design or not?
Does objective reality dictate that, design requires a designer?
Does objective reality dictate that for us to have a system which is designed to carry out specific instructions, based on a "blueprint", or a "structure" of precisely coded instructions needed to be communicated... that an intelligent 'mind' must be involved?
What objective reality is opposed to these?
I believe objective reality can be, and often is seen as such, based on subjectivity. So there is really perhaps a minuscule amount of objective reality where man is concerned.
However, I believe there is objective reality to the one(s) in the absolute position to know and determine it.
So objective reality is, but man knows very little about those realities.
For me, the reason I believe with 99.99% certainty that I have the truth, is based on many reasons, but one is mentioned here...
1 Timothy 4:7-10, 15, 16
7 But reject irreverent false stories, like those told by old women. On the other hand, train yourself with godly devotion as your aim.
8 For physical training is beneficial for a little, but godly devotion is beneficial for all things, as it holds promise of the life now and the life that is to come.
9 That statement is trustworthy and deserves full acceptance.
10 This is why we are working hard and exerting ourselves, because we have rested our hope on a living God, who is a Savior of all sorts of men, especially of faithful ones.
15 Ponder over these things; be absorbed in them, so that your advancement may be plainly seen by all people.
16 Pay constant attention to yourself and to your teaching. Persevere in these things, for by doing this you will save both yourself and those who listen to you.
In case you don't understand what the above is saying...
The statement, "For physical training is beneficial for a little, but
godly devotion is beneficial for all things, as it holds promise of the life now and the life that is to come."
is trustworthy and deserves full acceptance.
Why?
Because
we have rested our hope on a living God.
How do we know there is a living God?
Two reasons. 1. The "objective reality" that we see in the creative works of an intelligent designer, and 2. The information handed down by observers of "objective realities"... which has proven to be both reliable, and trustworthy.
We also have living proof of these realities.
Those I am not about to get into with you again. Concrete is a very hard substance. If it is well mixed, it takes a great deal of work and much energy to crack it, but steel... that needs a lot of time, and chemicals, to erode it. Or, we need a furnace.