Theory:

    “Number Two, your opinion please,” the President asked the scientist on the committee.

    “I recommend non-interference and passive observation. Since we do not know the power of the senders of these spacecraft, and we are still in the dark about their intentions, it is wise not to reveal our existence. If we destroy these spaceships or render them ineffective, we might reveal our existence.”
 
    The President looked at Number Three, a social scientist. He rarely agreed with Number Two. But this was one of those rare occasions when he did.

    “I agree with Number Two, sir. In fact I will go so far as to say that we should keep our surface activities to the minimum, thus creating the impression that there’s no life on this planet. Fortunately, our surface conditions do give that impression.”
Explanation:
 
The President asked the opinion of Number Two after hearing Number One's response. The committee's second member was a scientist. Later, the second scientist indicated that his suggestions were "not to interfere" and "observe things". It means that they did not know the power of the senders, and with the help of silent observation, they would analyse what it would be. Also, they were still in darkness about the intentions of the spacecraft. It means that they were not sure what their intention was, and the question remained unanswered. As a result, it was preferable not to divulge their presence on the planet.

Moreover, the second scientist added that they should keep their existence a secret because they have no idea about their objectives. If they destroy or make these spaceships ineffective, the spaceships may reveal their presence. It means that it was safe not to disclose their identity on the surface of the planet.

Later the President looked at the Number Three, and he was a social scientist. A social scientist is an expert in or student of human society and social relationships, or any subject within this field, such as economics or politics. Typically, the social scientist did not agree with the second scientist's points or suggestions. However, this was one of the rare situations when he agreed with the second. He also proposed that they should keep their surface operations to a bare minimum to the impression that the planet is lifeless. Also, if no one disabled or destroyed the spacecraft, it would, luckily, inform the senders that no one lived on this planet.
 
Meanings of the difficult words:
 
S.No
Words
Meanings
1
IneffectiveNot producing the effects or results that are wanted
2
Impression An idea, feeling, or opinion about something or someone, especially one formed without conscious thought or on the basis of little evidence
3
Non-interferenceFailure or refusal to intervene without invitation or necessity, especially in political matters
4
Passive Accepting or allowing what happens or what others do, without active response or resistance
5
IntentionA thing intended; an aim or plan
Reference:
National Council of Educational Research and Training (2007). Supplementary. An Alien Hand - Jayant Narlikar (66-73). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.