Here is a great example of a very well communicated post (albeit, on a very trivial topic):
Fried Egg said:
If we have ultimate control of all our actions, and if the ways in which our actions will interact with our environment are deterministically predictable,
then we have ultimate control of the consequences of our actions.
There are tacit premises here that will need to be made explicit. I'll try my best to guide you along. First, I'll simplify the language a bit, to avoid the possibility of an amphiboly fallacy. So let's reformulate the argument thus:
IF humans have control of their actions AND
the consequences of these actions can be known a priori,
THEN humans have control of the consequences of their actions.
We can then formulate it symbolically:
IF (H AND A), THEN C.
H=humans have control of their actions
A=the consequences of their actions can be known a priori
C=humans have control of the consequencs of their actions
Stated as such, you don't actually have an argument yet, but rather a hypothetical conditional proposition. We'll need to first remove the hypothetical IF . . . THEN (which is implicit in the structure of any argument already) and make a syllogism out of it:
Humans have control of their actions.
The consequences of human actions can be known.
Therefore, humans have control of the consequences of their actions.
Before we can evaluate the validity of this argument, let's first translate it into quantificational language:
For all x, IF x is a human action, THEN x can be controlled.
For all y, IF y is a consequence of human action, THEN y can be known.
Therefore, for all y, IF y is a consequence of human action, THEN y can be controlled.
We'll use these statement variables for complete translation into symbolic language:
H=human action
C=can be controlled
Q=consequence of human action
K=can be known
1. (x)(IF Hx, THEN Cx)
2. (x)(IF Qx, THEN Kx)
Therefore, (x)(IF Qx, THEN Cx)
After instantiation we get:
3. IF Ha, THEN Ca
4. IF Qa, THEN Ka
Therefore, IF Qa, THEN Ca
As of now, the argument is clearly invalid. Adding the premise IF Ka, THEN Ha would make it valid, but consider what that says: "If a can be known, THEN a is a human action." Obviously, that isn't true, so we should go another route. The best way I can think of is to insert the premise that Ha=Qa, that a human action is logically equivalent to the consequence of a human action. That is to say, if a human action occurs, then the consequence of that action naturally follows; one cannot be true without the other being true. So, now that we have added in your tacit premise, we can fully formulate your argument thus:
1. (x)(IF Hx, THEN Cx)
2. (x)(IF Qx, THEN Kx)
3. Hx=Qx
Therefore, IF Qx, THEN Cx
You can see now that the second premise actually isn't necessary to establish validity, so we'll just take it out.
1. (x)(IF Hx, THEN Cx)
2. Hx=Qx
Therefore, IF Qx, THEN Cx
Translated back into english, this says:
1. All human actions can be controlled.
2. All human actions imply their consequences and the consequences imply their actions.
Therefore, all consequences of human actions can be controlled.
(Premise 2 is basically saying that consequences are mechanistic, but saying it in such a way that the relationship between that fact and the subsequent control that can be exercised over the consequence is better illustrated.)