This blurs the lines
At the same time, having vague definitions of stealing, like "taking a fair/survival portion of something that is not rightfully owned is not stealing" also blurs the lines between what is stealing and what is not.
By defining it in such a manner, you create a top-down definition to which you have to now define what a "fair/survival portion" of something is.
Is taking a piece of bread when you're starving stealing?
How about taking some gourmet dishes from a restaurant?
What if that was the closest thing around?
What if there was nothing else around?
What if you had to choose between taking the gourmet dish, and putting your hand on the stove for 10 seconds?
If taking one piece of bread is not stealing, is taking two pieces of bread stealing?
How about three?
Four?
Onwards?
See how your answers change as these questions develop and try to develop some other scenarios. This tests the rigor of your definition and in turn tests the rationale thereof.
Thats the point though. I just wanted to point out that it isn't always so simple. All definitions of stealing fail in their own way.
With personal property its simple but beyond needs, everything is difficult to determine. The person taking it is in the best position to know if they are stealing but no one truly knows because no one knows who these things belong to. This is why its best to have restaurants setup like a local trend in my area. There are no prices and they simply ask "what would you like to pay for that today" and you make a donation. Most people pay normal prices but some pay much less, some pay much more, and no one steals.
Imagine the following for simplicity
1.there are 10 people in the world
2.only enough resources for 10 loaves of bread or less per week.
3. everyone needs a loaf per week to survive
Here is how it would work by my moral code.
-anyone who takes 2 or more loaves in one week is stealing no matter how they acquired the bread.
-taking 4 or less loaves of bread from someone who has made 5 loaves is not stealing unless you keep 2 or more for yourself.
-if someone gives you 2 loaves of bread and you keep both, you also stole one loaf of bread.
Of course its never that simple because our world has so many more variables and contexts at play. Its hard to determine what is stealing and what even is property.