The answer is that often you cannot.
For example, if someone says to you: "I've always wanted to ride a horse, but animals hate me," they could be suffering from a lack of Positive Self Image ("Rich people ride horses, I'm a second class citizen therefore I don't deserve to do this.") or they could have a strong Positive Self Image but be lacking in I-Can belief, ( "Animals hate me, they always have done.") or they could have a problem in both areas.
In the examples given throughout this chapter, the excuses could be caused by a lack of Positive Self Image belief OR a lack of I-Can belief.
The two are fairly closely linked anyway; that is why later in this book I give you methods which will dramatically raise BOTH types of belief together.
There ARE methods which you can use to spot which belief is most lacking:- If lack of Positive Self Image is the problem, then the actual excuse will be irrelevant. If you demolish one excuse by argument, another will be put in it's place. The 'brick wall' syndrome is more indicative of lack of Positive Self Image belief than lack of I-Can belief.
However, if the person offers one excuse and sticks to it; then shows an interest when you try to indicate ways in which they COULD achieve success; then lack of I-Can is likely to be the trouble.
Look at all the different types of I-Can't belief there are: