In order to keep the metaphysical statements out of the purview of empirical verifiability, metaphysicians claim that the assertions of metaphysics are not based upon the experiences of ordinary men; these are based upon the experiences of highly spiritual and elevated persons.
Being the experiences of highly elevated personages who have developed extraordinary powers of intuitive knowledge these judgments cannot be evaluated by ordinary rational standards.
The difficulty experienced by logical positivists in regard to metaphysics is precisely due to the fact that logical positivists subject the metaphysical assertions to empirical tests which are not applicable to metaphysics.
To illustrate, if a blind man were to reject the colour reports of normal persons because, he has no experience of these, it would be travesty of facts. The same is true of metaphysics.
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However, Carnap flatly rejects this line of argument. According to him no statement can earn the title of “meaningful until and unless it is fully supportable by empirical evidence which may confirm or disconfirm it.
The touchstone of every assertion is experience. If and only if an assertion can be reduced to such protocol statements which are directed about something immediately observable it can be considered to be meaningful.”