Gate of Doubt is the energy of logical questioning. It is the first step of analysis in the logic circuit. When the first cell phone was invented, this gate asked the questions, ''Is it safe? Will it work? Will people actually use them?'' This energy starts the drive to find the answer through logic. – source
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The Gate 63 contains the inspiration for logic. The 63 on its own is full of doubt and suspicion followed by a demand for proof. This particular gate can have some interesting challenges built into it. Doubt and suspicions are energies. And like all energies in the Human Design chart, they flow, almost reflexively. People with the gate 63 will have a tendency to be doubtful and suspicious of everything, including their own insights and abilities. Although, this is valuable process for logic, this can be a difficult personal energy. The doubt and suspicion expressed by the 63 is intended to be pointed towards information not towards people or towards yourself. When you see the 63 combined with the 48, a first line profile and an open Head and Ajna, you have a potent combination for mental paralysis and deep interpersonal inadequacy. Remember, these are collective energies and not at all intended to be expressed towards the self. The purpose of these energies is to correct the expression of information in the world. The other aspect of this doubt is recognizing that the doubt in the head is just a thought or idea and not necessarily true. It takes time to justify suspicion and doubt. You need proof. When you are out in the world freely expressing doubt and suspicion, is it usually met with resistance. Doubt is better left in your head until you have the data and you are asked to share. – source