John 10 & Eternal Security

I read with interest this morning an article at Arminian Perspectives titled - "Does Jesus Teach Unconditional Eternal Security in John 10:27-29?" (see here) in which the author sought to prove that these verses do not teach eternal security for the believer in Jesus. 

The writer makes the standard Arminian rebuttal by affirming that the security of the believer is conditional, rather than unconditional.  In other words, the believing and following of the sheep are the conditions of remaining saved.  The argument was then made that true believers and disciples may cease to be believers and disciples and thus not be finally saved. 
 
But, the writer failed to observe that the believing and following are not what make men sheep, but are what prove them to be so.  Believing and following are what sheep do because they are sheep, and not in order that they may become sheep. 
 
Besides, the "giving" of eternal life occurs when one becomes a believer and disciple.  It is not something that is given after death or at the day of judgment.  If I am a believer and disciple now, then Christ assures me that I have eternal life.  If one has eternal life, then certainly he has what cannot be lost.  If one could lose it, then it could hardly be called eternal life.  If Christ meant to convey the idea of a salvation and eternal life that was conditional, then he certainly would have not called it "eternal" life.  A life that is lost, or a life that dies, cannot be called eternal life.
 
Further, Jesus did not say - "some of my sheep continually hear my word and follow me," but "my sheep," all of them.  Thus, if all the sheep hear and follow, then how could it be said that some of them lost their eternal life? 
 
The idea of the passage is that once eternal life has been given, then it cannot be lost.  If eternal life can be lost once it has been given, then what guarantee is there that one will not be lost even after they have entered heaven?
 
Not only is the idea conveyed that no person can pluck them out of the Father's hand, but so can no thing do so.  This is what Paul taught in the end of Romans chapter 8 when he said that nothing will be able to separate the sheep from the love of Christ. 
 
Does not being in the hand of God protect from any and all danger?  Including sin and apostasy?
 
Whose responsibility is it to keep the sheep?  The sheep or the shepherd?  If it is the responsibility and duty of the shepherd to protect the sheep, and to secure them, then any destruction of the sheep would be the blame of the shepherd.  When a believer asks the Lord to save him from his sins, and the Lord agrees to do so, then he will certainly be saved or else the fault is with the Lord.  This is one reason why Paul said:
 
"Being confident of this very thing, that he which hath begun a good work in you will perform it until the day of Jesus Christ."  (Phil. 1: 6)
 
The shepherd of the sheep has a "rod" and a shepherd's "staff."  (Psa. 23: 4)  The staff has a crook for the purpose of pulling the sheep back when they begin to go astray.  I suggest that Jesus effectively uses his staff to prevent the sheep from leaving the fold and being destroyed by wolves.